Says who? Why are Republicans expected to win the presidency? Should Donald choose to run (which I doubt but he has to leave the possibility open otherwise money will flow away from him), why would he receive more votes than last time? He has not broadened his base.

DeSantis could well be the Republican nominee and formidable opposition for Democrats. His rise could spur the party to ditch both Biden and Harris who are all too qualified to lose. Buttigieg is the obvious good replacement, but there could be others.