Here's a fun thought.
President-elect Herbert Hoover gets blown up by an anarchist in Argentina (which nearly happened) and his Vice President Charles Curtis becomes President.
Curtis serves from 1929 to 1933, but is blocked at the 1933 convention and Coolidge gets drafted. Coolidge doesn't really campaign but manages to lose far less painfully than Hoover did OTL. Ohio, Michigan, New Jersey, Massachusetts, and Kansas all go for Coolidge and Coolidge loses to Roosevelt in 55-45 race.
Zangara proceeds to shoot Roosevelt, America freaks out as two president-elects in a row have been killed by anarchists, and Garner becomes President. Come 1936, Curtis clinches the nomination (Dawes as VP?). Despite what some think, Garner goes along with more than few of the OTL New Deal proposals (albeit in a more small-c conservative manner) and the result is that in 1936 there is more room for the Union Party to succeed. In a Curtis v Garner v (Lemke?) race, Curtis eeks it out.