About an SR government, the obvious problem is
which SR's? The party ranged from near-Bolsheviks to near-Kadets. Even the secession of the Left SR's did not really give the party ideological coherence. The Party of Socialists-Revolutionaries (PSR) after the secession is often referred to as the "Right SR's" but this is misleading; may of its leaders like Chernov could better be described as center or even center-left SR's.
Furthermore, contrary to popular belied, the PSR did
not win a majority of the vote in the Constituent Assembly election. In a post a few years ago,
https://www.alternatehistory.com/forum/threads/wi-lenin-dies-circa-august-1917.342336/#post-10253193 I explain why this is a myth:
"Sviatitsky claimed about 400 deputies for the Populist camp (leaving aside the Left SRs) but of these he actually only claimed 299 for his own party, the SRs. The remainder of the 400 were *Ukrainian* Socialist Revolutionaries (81) or smaller SR national groups (19--Moslem, Chuvash, Moldavian, and Buryat).
"It is a great mistake to assume that these one hundred deputies would necessarily vote with the (Russian) PSR. Moslem SRs, like other Moslems, did not share the Russian Populist intellectuals' enthusiasm for the war and the Allies. (One Moslem SR from Ufa province not only supported the Soviet government's peace initiative but criticized it for not moving even faster in that direction.) And the Ukrainian SR party was not only organizationally separate from the PSR but had its own agenda, which, while it did not yet call for outright separation of Ukraine from Russia, nevertheless carried self-determination and devolution to a point much further than the PSR would be likely to accept."
Second, the Assembly which actually met was almost a rump Assembly: "The Assembly was supposed to have over 800 members, yet only 703 or 707 were elected. Part of the explanation is that in twelve electoral districts, mostly in Central Asia, the election never came off. This accounts for either 81 or 86 of the vacancies. The bulk of them would have gone to Moslem nationalists, who would hardly be likely to agree with the SRs' enthusiasm for England and France (nations which Russian Moslems saw as oppressors of Moslems in Asia and Africa) or for the Armenians--or for the strong SR antagonism toward Turkey and Turkey's German allies..."
Even among the deputies who were actually elected, many were not present:
"Another point is the large number of deputies absent on January 5. (Of course, one cannot blame some of the deputies for fearing that going to Petrograd would be a ticket to jail or worse. The Bolsheviks had already outlawed the Kadets, for example.) Radkey gives three different sources' estimates of the number of deputies present: one gives 427, another 402, still another "around 500." (In his essay "The Constituent Assembly" in Edward Acton, Vladimir Iu. Cherniaev, and William P. Rosenberg, eds, *Critical Companion to the Russian Revolution*, Nikolai N. Smirnov writes that "at least 410 deputies took their seats." p. 331) Since there were supposed to be slightly more than 800 deputies, it seems likely that almost half the membership was absent, either through failure to get there or failure to be elected. Note, for example, that Chernov was elected chairman by 244 votes in his favor to 151 against; Spiridonova's candidacy got 153 affirmative and 244 negative votes. In other words, this crucial test of strength did not involve even half the membership of the Assembly.
"Most notably the Ukrainian SRs were not at the Tauride Palace; their party's Central Committee had decided that the deputies were needed in Ukraine, where the Rada had called its own (Ukrainian) Constituent Assembly. A few Ukrainian SR deputies did go to Petrograd to announce to the All-Russian Assembly that they would not participate in it, but reserved the right to do so in the future! (As Radkey puts it, "In other words, if the assembly were a failure, they did not wish to be involved, but if it succeeded, and came to wield authority, they would take their seats." p. 389)…
Radkey's conclusion: "In dissolving the Constituent Assembly, Lenin was putting an end to a body that would likely have fallen of its own weight. But he was scarcely destroying a nest of counterrevolution, as he and his comrades have so often proclaimed. He had hastened to strike down the specter of right SR control arising out of the half assembly of January, 1918, without waiting for the full assembly to convene. In such an assembly, with all members elected and present, there would have been a majority for peace and one for recasting the conquered empire of the tsars along lines of broad national autonomy. There would have been no majority for restoring the discredited Provisional Government. The right SR's with their contraband Kadetism would not have ruled this assembly, grossly overrepresented as they were. With all of its imperfections, chief among them this Trojan horse of counterrevolution in SR trappings, the Constituent Assembly was nevertheless an authentic expression of the hopes and hatreds of the populations residing within the Russian Empire..." *The Sickle Under the Hammer: The Russian Socialist Revolutionaries in the Early Months of the Soviet Rule*, p. 463.