Do you mean winning a general election as a third-party or independent candidate? Nobody has ever come close to doing that, but there have been several major spoilers. Ralph Nader, for example, cost Al Gore Florida and the presidency. Theodore Roosevelt took second place as a progressive in 1912 with 27% of the vote, beating the Republican contender, but as my BIL likes to say "second place is first loser." H Ross Perot got 19% of the popular vote in 1992 and people thought a viable third party was being born.Rumpy wrote: Thu Sep 14, 2023 7:37 pm What happens if an Independent wins in the U.S? I think Bernie Sanders got the closest. That's more of a likelihood in Canada with its myriad of parties
If you mean an independent taking the nomination from one of the established parties, that could describe trump, who was neither a politician nor a partisan before he took over the R Party. His political convictions are only what will benefit him personally and Republicans were already leaning authoritarian after losing to Obama. Before trump upset their apple cart, it looked like they were going to nominate another Bush (Jeb). Trump could just as well have tried to capture the Democratic Party. Would he have fizzled out early if he'd gone that route, or would he have snatched the nomination from the reviled Hillary Clinton? (Unlikely, since she had a firm grip on the party machinery and Democrats are less susceptible to snake oil, but it's not impossible.)
Anyway, the short answer to your question is trump happened.