The only person capable of fracturing the Republican base is Donald Trump himself, by refusing to endorse DeSantis should he lose the primary, or worse, deciding to run as an Independent in the general election. Sadly, both of these potential outcomes are well-within the realm of possibility given what we know about Trump's fragile ego and well-documented pattern of vindictive and petty behavior. Conversely, if Trump defeats DeSantis in the primary, I have zero doubt that DeSantis would readily endorse Trump. As for Trump's hardcore base, they are not exactly known for their independent judgment and critical thinking skills (about what you would expect from a group consisting primarily of half-senile boomers, QAnon true believers and an assortment of credulous marks who can rationalize away all of Trump's glaring faults and failures). In the end, they'll do whatever their leader Trump tells them to do, because that is how the members of a personality cult behave.Secondly he's only going to fracture the base which is 100 percent what the Dems and Soros want. This is all obviously part of there agenda and something Soros openly spoke about. Doesn't mean Ron's in on it..But he would effectively create a Buchanan/Ross Perot type split among the Republican party IF he beat Trump.
Thirdly it's irrelevant what Donald would or wouldn't do as far as endorsements go. His base of voters will not show up and vote for the challenger who ousted him. They will stay home.