I'm going to hazard some guesses:
- With Roosevelt being strongly pro-war, the Progressives will essentially absorb the Republican party and shed much of its progressive base.
- Bryan runs, and picks up most of these, while Seidel does pretty well too.
- Bryan gets elected president, and find his hands tied, in that he has to somehow bring the war to an acceptable conclusion. He wouldn't be able to simply back out in a status quo ante bellum peace, as that would anger Americans who spilled their blood for nothing, and he can't demand enough until Britain has bled enough to accept losses.
- Even if he puts together a treaty that his base can accept, the Senate might fail to meet the 2/3rds threshold to pass it, if enough senators are pro-war, while some radicals might even reject a treaty that involves any annexations whatsoever due to it being an unjust imperialist war. Could there even be a movement to impeach for failing to prosecute the war in the full interests of the American people? Not that it would be likely to even pass the house, of course.
- The war will drag on until 1920, somehow, and be a key issue in the election once again. Could a peace by exhaustion, approaching the final stretch of the election campaign, see the American people up in arms with the feeling that the war was an unmitigated disaster? Perhaps the Senate refuses to ratify the final peace treaty (just like Versailles OTL) due to the desire for a more favorable settlement.
- The Socialists could be the champions of women's suffrage, and reap the benefits of organized registration and turnout of sympathetic women
- The Socialist candidate gets a huge plurality of the electoral votes, but not quite a majority outright.
- The threat of a corrupt bargain combines with the threat that the government will somehow restart the war, with radicalized socialist divisions held under arms at the Canadian front or in the Russian expeditionary force, keeping them from returning home to vote, while the armistice threatens to time out.
- Wildcat actions become organized into a nationwide general strike. Marches for peace and democracy coincide with the organization of mutual aid to provide necessities.
- Negotiations for the corrupt bargain break down, but as yet there's still deadlock. Many intransigents would rather play chicken with the strike and let the oncoming winter force them to give in, while other congressmen are already uncomfortable participants in the corrupt bargain and see the strike as an excuse to back down.
- Recent winters have been quite cold, but as it turns out that the winter of 1920-21 is, on the contrary, rather warm, the strike holds up well enough that public pressure and political negotiations manage to pull just enough state delegations to give the presidency to the socialists.
So, how wildly off-base am I
?