Would have done one for 1930, but the severe drought that would later kick off the dust storms probably would have had the same effect for Hoover in the Midwest, and it would be a wash.
1918President Woodrow Wilson (D-NJ) / Vice President Thomas Marshall (D-IN)
Fmr. Governor Charles Hughes (R-OH) / Congressman Irvine Lenroot (R-WI) ✓
There's a huge drop in turnout as the flu disrupts campaigning around the country and millions of men are busy fighting overseas. The midterms OTL were a backlash rather than a rally 'round the flag- sorry Wilson hacks- but not as strong of one as 1920, when the global economy fell very sharply from the mild retreat of 1918 and what rallying 'round the flag there was had dissipated. I think he loses a close-ish one with the war clearly days away from ending, and it's not really seen as a changing horses mid-race thing like a presidential election in 1917 might have been. Hughes is probably the Republicans' nominee; he was open to the prospect of another run before the death of his daughter in 1920, and Roosevelt's health had declined seriously by 1918. Debs also does better earlier on in the Red Scare.
1958Senator John Kennedy (D-MA) / Senator Lyndon Johnson (D-TX) ✓
Vice President Richard Nixon (R-CA) / Ambassador Henry Lodge (R-MA)
1958 recession. Humphrey might have been the nominee, but the map would be similar enough.