I really can't see Schumacher being elected if everything else stays more or less as OTL.
OK, what if it isn't more or less like OTL--that is, the general pattern of Germany going Nazi happens, the Grand Alliance of Soviet Union with Commonwealth and USA does happen, victory of the Allies happens pretty much as OTL--but the character of the Western Allies is different, and more socialistic?
Quick outline of a POD and developments mainly focusing on the USA here:
1) Theodore Roosevelt does not challenge Taft for Taft's reelection in 1912. This is most easily accomplished by TR not surviving his world tour after he handed over the Presidency to Taft in 1909--he dies on safari maybe, or just catches some disease somewhere, he didn't last to 1920 or IIRC even 1916 OTL after all. So Taft stays the course and a sufficient majority of voters vote Republican--if we take the combined popular votes for both TR and Taft OTL, we can whittle them down a lot and still have Taft win the EV--probably with a small but solid PR plurality as usual.
2) Taft, being the weak fellow he was (many suggest the main driver of Taft's career was his wife's overweening ambition, basically henpecking him into attempting things way out of his comfort zone) continues to be basically the compliant tool of the corporate wing of the Republicans, and many disparate factions not so well allied to each other but reformist to revolutionary and quite disgruntled continue to build up steam. In 1912 for instance I'd suggest some people, not a lot but some, who voted for TR switch to backing Eugene Debs instead, and there are yet more Republicans of OTL who vote for reformist progressive Republicans--I am not sure if Robert LaFollette can be the man, but maybe. The reformist to revolutionary spectrum is by no means strong enough, even if unified as they won't be, to command majorities, but they are influential and have some considerable power in some locations and sectors.
Taft accordingly bows to orchestrated business-Republican interests who want in on the Great War which develops as OTL without regard to Yankee affairs, until the USA comes in on the Entente side but on different terms, well before Taft must leave office in 1917. Another Republican gets elected on a jingoistic platform. Woodrow Wilson is an also-ran flash in the pan and the several Amendments and other reforms of the OTL Wilson years are deferred. But some of their subjects make progress anyway--women's franchise was achieved to a large degree on state by state initiative for instance, Prohibition might never happen on a Federal level but be quite strong in swathes of states and Federal authorities might have legal leeway to assist these states; direct state election of Senators was something that actually the states could have done piecemeal, there is no Constitutional barrier--to my surprise, unlike women's franchise, no states actually tried it until just a handful of years before the Federal amendment passed, but a few did take that step and in the ATL I suspect quite a few states would institute it Amendment or no Amendment. Federal Income Tax would require an amendment, and perhaps the hawkish corporate Republicans would want it and smooth the way for a version of that Amendment alone, or perhaps devise a workaround according to the Constitution, which limited Congress to the option of a head tax on the states, meaning each state would have to pay according to population without reference to income. This would not be popular in the poorer states (but might be in the states with higher per capita incomes) but it might be deemed Constitutional, or simply left unchallenged, to devise some scheme whereby on a "voluntary" interstate compact basis, the richer states subsidize the poorer ones to equalize the burden to de facto be a state proportional wealth tax. (Note, this apparently radical idea was exactly the formula the Articles of Confederation imposed on the states--it failed because the Continental Congress had no means of compelling the states to comply, which moots the question of how politically sustainable a claim to assess the wealth of the various states would be--I suspect it might work about as well politically as the income tax did. The question of how each state would raise its share of the nominal head tax would presumably be left to the states in principle, though model legislation might be a guideline most states follow. The more radical states might well go in for a strongly graduated income tax or wealth tax, the more conservative ones lean on a "flat" income tax or even sales or other regressive taxes, including a highly regressive head tax maybe).
The USA enters the Great War with a lot of fanfare and jingoistic persecution of dissidents, as with Wilson's handling of it OTL.
Then the war does not go so well. There is no way I think the Entente can lose with the Yanks coming, but perhaps the Republicans badly mishandle issues of strategy and diplomacy, and US doughboys go into the trench war meatgrinder in a way that eventually has major political repercussions at home. Not immediately, of course, wartime censorship is effective, and the Entente will win, pretty much on OTL terms. But the onus of the dark side of the Great War is on the hitherto ascendent conservative Republicans and their Dixiecrat allies.
3) therefore there is a strong left-progressive reaction when the dust settles, and the boys come home and vote. This has effects south of the Mason-Dixon line as well as north; not every "white" southern state electorate is equally under the spell of Jim Crow and general Lost Causer mythology. There are radicals who can see through the mythology and champion various more or less pragmatic progressive alliances, some working within state Democratic establishments they take over, others in bold opposition which occasionally succeeds. Rarely if ever does this involve even progressive Republican ascendency, usually it is some new third party or some party still claiming the Democratic mantle, and plenty of reaction still holds sway over much of the South. But not all of it! In the north and west the ascendency of various progressives is more straightforward, and it is compromised by opportunistic corporate sector types who see that they had better try to ride this whirlwind rather than try to repress it.
4) I often note that OTL, the electoral reform of Single Transferable Vote is overlooked, but in fact it prevailed in a great many US cities in the period between 1900 and the Cold War, around 1950, eventually such cities as New York City went STV for their city councils. What if instead of stagnating and eventually being demonized as a Red plot, the trend redoubles and various states go over to STV for state legislatures and electing their Representative delegations? (Such states would presumably make election of their federal Senators by Instant Runoff Voting, which is the single-seat implementation of the STV mechanism, and probably such offices as state governor and other statewide single person offices too). At this point the movement involves no formal reforms in Congress; per the Constitution, Congress devises a "population proportional" means, guided by the US decennial Census, to allocate Representative seats to the states, and then (until the Civil Rights era of the 1950s-60s OTL) SCOTUS and other authorities held it was up to the states to decide how they would popularly elect these Representatives. In 1952 OTL for instance, several states elected one of their delegation at large, and two elected two by running both at large. So no Constitutional impediment exists in a state that is granted say 9 Representatives to decide to divide itself into three districts which each elect three Representatives by STV. (OTL, in the Civil Rights era, between various precedent breaking SCOTUS and lower federal and state court rulings, and legislation in compliance with these court rulings enacted by Congress, invoking its authority to judge its own elections, the rule was laid down that all Representatives must be elected in single member districts, though not specifying FPTP which was merely assumed--states can still decide to use a different mechanism than FPTP, such as IRV, to elect each member, and Maine has done this).
Thus, if STV and perhaps some alternative voting reforms in rivalry or combination, becomes a popular reform plank, in the ATL early to mid 1920s reacting strongly against conservative ascendency seen as dragging the USA unwisely into the Great War plus a whole head of steam of other reformist causes, we might see quite a lot of states switching over to these non-FPTP methods, which would tend to make the House of Representatives more proportional, and tend to enable rival parties to the Republican-Democratic duopoly to establish themselves on a long term national basis, probably with most of them having a specific regional bastion to be sure. Enough of that, and neither mainstream duopoly party would have a majority in the House and perhaps with enough third party Senators being elected, not in the Senate either, forcing a change of rules for how the Houses operate recognizing the wider distribution of partisan power.
Thus, I think we can postpone and amplify the reformism of the mid-1910s to the early to mid 1920s.
Perhaps it can be justly argued that conservative influences remain strong enough for the conservatives to make a comeback by the later 1920s, but I don't think they'd be able to, or much inclined to, roll back the progressive reforms wholesale.
5) then as OTL the Great Depression hits. Now some people are of the opinion that things like the Depression are easily butterflied; I hold a quite different view that the basic cycle of boom and bust is deeply embedded in capitalism, and that the more irregular cycle of generations of general recession (weak booms, long deep depressions) versus buoyant periods (short and mild depressions, long and broad booms) also is grounded in deep factors that are quite hard to butterfly. I believe proximate causes of crashes we identify as "the cause" can be shifted around, magnitudes of depths and heights reached in troughs and booms varied somewhat, but overall the broad width and depth of economic waves is pretty well fixed.
Meanwhile, if we want the late 1940s to be broadly similar to OTL, we surely do better to stipulate this theory of broad and deep persistence of economic trends under capitalism!
6) the Republicans and conservative Democrats (and perhaps conservative to moderate third party allies) having recently and weakly regained ascendency, and some Republican president of the Hoover type (perhaps not improbably Herbert Hoover himself, he'd pass muster of moderate reformists pretty well, probably better than Calvin Coolidge would have certainly in the ATL 1924) fumbles the ball with predictable conservative hidebound ideology. Now perhaps the Hawley-Smoot Tariff which many of the more butterflyable persuasion like to blame for the length and depth of the Depression would not pass in similar form, but some other error of fiscal policy (as seen in retrospect) does comparable damage. Or HS passes essentially as is. Or no such egregious fumble is inflicted by Congress but the Depression turns out to be a huge crash anyway.
It would be at this point that we have AtL respectability of various diverse parties that are more or less socialist (shored up by strong social democracy and moderate but pragmatic liberalism) could build up momentum to take the House back in 1930 and the Presidency for a forthrightly social democratic/socialist candidate in 1932. Instead of FDR we have an ATL populist wave for a more forthright radicalism that steamrollers politically over conservative opposition, making compromises with the corporate sectors that buy their acceptance and in some cases even recruit some to positive support for a much more proactive public involvement in the economy. Thus, the American left cements itself about as well as FDR did OTL as a more radical New Deal.
7) for reasons broadly similar to FDRs, perhaps with more emphasis on democratic idealism and less on realpolitik power, the leftists in ascendency oppose European fascism and Japanese militarism, and support various factions of Chinese republicanism. Thus, belatedly as OTL, the USA enters WWII. It is possible that by the time the USA does enter the war, the moderate right has made another comeback and it is some moderate Republican of the Dewey type who is running the US war effort. But whether or not the nominal Presidency in the year of European victory is an actual elected Socialist, or is a conservative opponent, even the latter cannot silence or quell a broad support for leftist social democracy in the USA whose victory would probably be seen by many as a victory for economic democracy supporting political democracy.
Meanwhile in the Commonwealth, whether or not the stronger fortunes of American leftists have any bearing on Parliament before Britain enters the war and before Churchill forms a War Cabinet inviting in Labour to govern alongside Conservatives and Liberals, we have little reason to doubt the British electorate with its Services Vote would also veer left just as in OTL, and it is quite possible that despite conservative notions even a Republican US President will have a clear mandated demand from the American electorate to assist a Labour leaning Commonwealth.
Would this necessarily butterfly away the Cold War? I think not; the American leftists are on a spectrum that surely would include some Third Internationalist Communists obedient to the Kremlin line. But these would hardly be the majority of the left! A much larger portion would range from a peculiar mix of conservative and progressive planks (like the OTL Prohibition party) to a pretty hard line socialistic but still distinctly Second International bunch of Socialists, and probably there would be some Trotskyite Fourth Internationalists too. The Comintern Reds might well achieve a greater degree of electoral legitimacy and somewhat broader support, but many who joined with them as at least fair weather friends in the '30s might veer instead into the Debs-Norman Thomas Socialists, or jump right over to Trotskyism. The latter are likely to get into serious trouble with US reactionary forces finding plenty of pretexts to ban and persecute them, but the former would be under cover of respectable American practices so long as they don't attempt violent or otherwise criminal methods. And even card carrying Communists might find their political rights better protected, as long as they are individuals who cannot be prosecuted with evidence beyond reasonable doubt of specific criminal acts.
If Stalin is as OTL, I would expect a broad national patriotic line of friendship for the Soviet Union during the war, in which many leftists outside the CP are if anything more skeptical and queasy about it that the reactionaries are, followed by most US leftists being disillusioned (many feeling it vindicated their doubts they held all along) at Soviet behavior postwar. A firm anti-Communist line might form that does not react against socialism (or such reforms as STV, or civil rights) in general, with socialist leaders taking an early and firm stand against Stalin's brand of Red imperialism.
Meanwhile, in London, and in other Commonwealth capitals, we can expect moderate leftism to be riding high too, significantly higher even than OTL if US policy supports the leftist Commonwealth policies with various forms of both moral and material aid.
In France, it is only OTL to note that the Left tended to prevail in the Fourth Republic's governments.
So now, it is 1949, time to launch a new Federal Republic of Germany under domestic leadership after 4 years of de-Nazification that probably went a lot stronger than OTL or somewhat so anyway.
The Christian Democrats, their moderate-conservative candidates having undergone stricter scrutiny, might be in quite a weaker position, along with the other moderate-conservative parties. The Social Democrats, known foes of Naziism who paid dearly for their opposition to Hitler, are more in tune with the ATL US political spectrum as well as with the British and French ruling parties.
It seems entirely likely in such circumstances, that it would be an SD who wins the Chancellorship first and defines the nature of West German politics into the foreseeable future, and such a regime would be a fine ally in the ATL version of NATO.
