We have talked a lot about otherwise plausible presidential candidates (e.g., Carl Schurz, John Peter Altgeld, Robert F. Wagner I, Arnold Schwarzenegger, and Jennifer Granholm) disqualified by the "natural born citzen" requirement. Can we think of any who were disqualified by the "at least 35 years old" requirement? The only plausible one I can think of offhand is Harold Stassen (born in 1907) in 1940. OK, maybe Joe Biden in 1976, but that's a pretty long shot. And just possibly a deadlocked GOP convention in 1920--when Theodore Roosevelt would probably have gotten the presidential nomination had he still been alive--turns to Theodore Roosevelt, Jr.
(Another possibility: If LBJ is killed with JFK in 1963, there may be widespread support for the idea that McCormack should serve only as interim president, and that a Kennedy be nominated in 1964--but of course that will be Robert Kennedy, not his younger brother. Unless RFK too dies by 1964--but having all these deaths sounds a little implausible.)
I'm putting this in the post-1900 section because all of the examples I can think of are from post-1900, but if you can think of any earlier possibilities, that's fine.
(Another possibility: If LBJ is killed with JFK in 1963, there may be widespread support for the idea that McCormack should serve only as interim president, and that a Kennedy be nominated in 1964--but of course that will be Robert Kennedy, not his younger brother. Unless RFK too dies by 1964--but having all these deaths sounds a little implausible.)
I'm putting this in the post-1900 section because all of the examples I can think of are from post-1900, but if you can think of any earlier possibilities, that's fine.