Roosevelt served two terms and retired, groomed and endorsed his successor, William Taft who won in 1908, and then tried to form the Bull Moose party in 1912. He did so after losing the Republican nomination in 1912. There was no way a majority of Republicans were going to abandon an incumbent President.
Trump has 75% of the party behind him and coming off an election where he got more votes than any incumbent President in history. He's in a much better position than Roosevelt was in 2012.
See comment above about deck chairs.
But this also might be the time to pull the plug on the GOP, and Trump might be the guy to do it.