IMO the best possible case scenario here is DeSantis and Trump remain so close that they go into the convention without a clear winner. Then the GOP tips the scale in favor of DeSantis because he's the more establishment-friendly candidate and Trump decides to run 3rd party out of spite. He gets on the ballot in just enough sympathetic red states and inspires just enough down-ballot 3rd party challengers to run as "Trump party" options that the GOP suffers a historically embarrassing loss up and down the ballot across the country. Then Democrats get actual concrete majorities both in several states and federally and the younger more progressive members drag some of the dinosaurs kicking and screaming into reestablishing a right to abortion access, reinforcing voting access rights, reforming campaign finance laws, reapportioning the House to be actually a representation of the population like the Constitution says it is, and expanding the SCOTUS to 13 seats so they can't legislate away any of these reforms from the bench.
Of course the odds of that happening aren't actually very good, it seems much more likely we're just going to get a Trump primary victory followed by another contentious general election, a narrow Biden reelection amidst threats of violence (and possibly J6 repeats), and basically these last two years all over again with stubborn center-right Dems crippling the Senate agenda while Republicans cling to a very narrow majority in the House and basically shit up the Congressional session with pointless hearings for political theater, threats of crashing the entire economy out of spite, and otherwise throwing up non-stop hurdles in front of attempts to address even the most basic, non-controversial issues facing normal people in day to day life. Basically the only thing Republicans are good at, making government as dysfunctional as possible. Still preferable to a DeSantis presidency though. Complete dysfunction for two years beats christofascist authoritarianism.