Many people, for example Ben Shapiro, are pushing for Desantis or Nikki Haley to win the primary. Of course, Trump’s lead is insurmountable, and anyone who thinks otherwise is just not aware of Trump’s popularity with much of the Republican base: Indeed, the insults the left constantly levies against Trump supporters has made them hungry for redemption. Ironically, they attacked MAGA Republicans too hard: There is a point where oppression actually can solidify and strengthen a movement.
However, if Desantis or Haley were to win, Biden would likely pull out. Biden is staying in because he does not want to be perceived as running away from Trump. So, the relevant statistic is not how Desantis or Haley do against Biden, but how likely Biden is to pull out in the event either wins and how they would do against an alternate Democratic candidate.
For starters, much of the Trump base might refuse to turn out if Trump is not the nominee. Secondarily, the Democrats might nominate another “revolutionary candidate” like Obama, i.e. a person of color, who could increase enthusiasm among a core Democratic constituency.
Without tackling these probabilities, it would be tremendously unwise to abandon Trump when the most recently polling suggests that he has a slightly better than 50/50 shot to win: And momentum seems to be favoring him .
Trump should have supported De Santis instead of running, but given that Trump chose to run it's ignoble of De Santis to run against him. They've both acted badly -- Trump for running, De Santis for running against Trump. And at this point any vote against Trump in the primary would be seen as a sign of submission to the Empire's vicious rulers -- but this leaves the option of not voting in the primary still morally available.