I did a little research. The DOJ can request that she recuse herself, but she can refuse, which is probably the case. Then the chief justice of the southern district of Florida would weigh in. She is a Bush appointee and probably a Republican. She may uphold Cannon's refusal.

Something else that I came across is that the assignment of judges depends a lot on scheduling. There may literally be no one else who is free to oversee the case.

And then, regardless of who the judge is, all it will take is one not guilty vote on the jury and Trump will walk out of the courtroom a free man.