I wouldn’t say that, without the “radicalness” of McGovern and the dropping of Eagleton along with HHH’s great campaign skills (look at the 1972 turnaround), it would be much, much closer. If Wallace without being shot runs as a third party or the peace talk/Watergate scandals coming out, I think Humphrey could win.
This is one of those rare moments, of which I will say I'm not fond, where I disagree with
@Oppo. I suspect that with a martyred McGovern in particular, HHH as the guy who lost last time and, as in '68, gets perceived as shorting the New Left on its dream so its voters stay home, which is one of the constellation of factors that cost Humphrey (who I adore, I would add) the '68 cycle. I suspect that a campaign-competent Muskie especially, or even a McGovern without an Eagleton scandal or Humphrey's Nixonian assault on McGovern in the California debates (again Humphrey lover here but that was the nastiest thing he did in his whole political career, all out of fear that he would die soon of the family tendency to bladder cancer and this was his last chance), would stand a chance with Wallace as a third-party candidate. Of course IOTL Nixon actually sat down in two days of meetings that have no official records with Wallace late in '71 and essentially told him to run as a Democrat in order to screw with the field and then drop out, or Nixon would put Wallace's brother Gerald and possibly George himself in prison through an IRS investigation into their tax irregularities. Now, if you take a POD dear to my heart and (1) cause what we could call an accelerant (as the fire inspectors do in cases of arson) to the constellation of symptoms we call "Watergate" and (2) convince a Wallace who
has been shot by Bremer and paralyzed that revenge is the best kind of living well and that, given the mess swirling around Nixon he can claim the IRS charges are dirty tricks, then either of them (Muskie especially but also McGovern) has a shot. Because old George Corley in particular thinks
this time he really can hang the Electoral College.
In the OP, McGovern would indeed become a martyr for the New Left and you're going to have to put at least one person on the '76 ticket with whom they feel comfortable. There will be more liberal mobilization in '76. and perhaps more sense that they need to cohere around a candidate, the question is just who that candidate will be. I would
love to see Birch Bayh as POTUS but he proved pretty conclusively in '76 that he couldn't campaign his way out of a paper bag at the presidential level. At a very personal level I'd like to see Mo Udall take '76, serve two terms, and make the national GOP self-radicalize into irrelevance like the California GOP of the later Nineties and Aughts. But he's still going to have to face either Carter or someone very like him, and many tribally-Democratic Southerners and socially moderate-to-conservative Midwestern union members who would like someone not
too comfortable with the well-heeled longhairs. The best bet at avoiding Reagan and the very genuine radicalization of American politics (Nixon plowed the rows but Reagan watered and fed the crops vigorously) really is that Gerry Ford (or his functional equivalent as the Twenty-Fifth-authorized VP after Agnew) wins in '76 and gets to own the whole "kidney stone of a decade" in Gary Trudeau's famous phrase. That gets you (1) a Democratic president acceptable to the whole big tent and (2) more wind under the sails of the liberal-to-left wing of the party for their long term prospects. They have, ITTL, never
failed with Bobby, or going Clean for Gene, or the remarkable run of George McGovern before its tragic end. They have only been
denied and that's exactly the kind of ammunition that fueled the New Right, for example. In time that may give them a realistic shot if they can find a candidate with enough stones and a pragmatic streak on the campaign trail. Down the line I would back people like Wellstone, Barbara Boxer, a surviving Mickey Leland, but with a 1972 POD your mileage may vary considerably.