Presidents of the U.S. listed in a timeline graph of elections with results of the popular vote color coded for political parties. A gray arrow points to the name of a person who became president without having been elected as president (9 total). The double arrow indicates becoming president without having been elected as vice president as well (Ford). 5 other former vice presidents are underlined (14 total). The top line indicates the Presidency number (e.g. Reagan: 40th) with Roman numerals indicating election (and term) number.
You’re aiming at the wrong place. Government is made at lower levels. The place we need to break the duopoly first is the state legislatures. Get a 3rd and even 4th voice there and you can end gerrymandering. End that and you can get these other voices in Congress. Then you’ll make ALL the parties actually stand for something other than power. And the presidency can actually matter.