I don't know which way this is trending yet. Some polls have shown DeSantis with a lead over Trump in some places and some have shown him waaay behind Trump. My own take is that DeSantis won't pull mainline Trump supporters, So the question is how big a proportion of Romney's 2008 GOP numbers are the poeople who won't vote for Trump but haven't gone full party repudiation?
Guys like David Brooks for instance, still want to vote GOP in the worst way if any non-Trumper would run - he was talking up GOP governors the other day. But DeSantis is too far over the line for him. If DeSantis can't pull in a 'moderate' GOP voter already highly disposed to the GOP, he'll have trouble beating Trump just with hard core culture warriors, I see them mostly sticking with Trump.