I don’t recall having a party with a President in office running a differant canidate when that pres is up for re-election. Is there a historicial presadent?
I think it was going to happen with LBJ but he quit. Otherwise I don’t know.
I don't know of a case where a challenger won the nomination against a sitting president, but Ted Kennedy challenged Carter for the nomination in 1980. The resulting battle at least gets some credit for fracturing the democratic base and boosting Reagan. Which is why I seriously doubt she'll run.