Primaries are kind of a moot point for the incumbent if they want to run again.
Trump in 2020 had 2,549 delegates. The next closest was Bill Weld with 1.
Biden in 2024 had 3,905 delegates. The next closest was uncommitted with 37.
Obama in 2012 had 3,514 delegates. The next closest there was also uncommitted, with 72.
Bush in 2004 had a clean delegate sweep of 2,509.
There'd have to be a primary challenger who beat the incumbent first, and I don't think that one has happened. I know Ted Kennedy got relatively close (Well, closer then the others I've mentioned, still blown out 1900 to 1200 delegates) to knocking out Carter on the Dem side, other then that, Reagan and Ford in 1976 was decided 1,121 to 1078 for Ford.