It's a good strategy, and probably the only one that could unseat Trump.
President Trump as a concept was a great idea. But, we have to admit that sometimes Trump wasn't all that great at Trump-ing. If DeSantis plays the where's-the-wall card, it will ring true. Especially with DeSantis record as a doer, not just a talker, on immigration.
DeSantis is vulnerable two future accusations: One, that he will be beholden to the establishment GOP, and two that he has a past of sexual harassment, sex with young girls, and/or affairs.
The first probably has a grain of truth. The Establishment would back him if he could help them get rid of Trump. He would be beholden, and if he promises them things for their support, he won't renege.
The second needs no grain of truth. Nay, not even a mustard seed of truth. The Dems can simply manufacture witnesses to come forward, similar to Blasey-Ford and the media will run with it. My prediction is that the will combine all three by having a woman "come forward" with a report of forced sexual assault short of rape of her as a minor teen while DeSantis wife was pregnant.