My belief is that Crist is going to leave the GOP and go Independent on his way to switching to the Democrats in the next four years, perhaps to try and run again for Governor. Which means he's going to drop out of the race for the Senate and concentrate his attention on making sure Rubio loses.
The fact is that, thanks to his SB6 veto - if not his support for the Stimulus - his career in politics as a Republican in Florida is, for all intents and purposes, over. This race is his best chance of winning any office as an Independent so if he doesn't succeed, the only other option is for him to become a Democrat - he is not ever going to win a Republican primary.
Kendrick Meek is a non-entity in this race for the moment, but that could change if Crist throws his support behind him. The media would love it and both Meek and Crist would dominate a few newscycles - it gives them another excuse to promote the Republicans are intolerant lock-step marching dittoheads meme, and since Meek is black, of course, racist.
The fact is that Crist has basically trapped himself. He has nowhere else to go if he wants to stay in electoral politics.
If Crist decides to remain in the race as a Republican, he will lose. If he decides to launch an Independent bid, Crist's only path to victory lies in keeping his supporters and drawing the more ignorant Independents to his side by tarring Rubio, thus his calls for the Feds to investigate the FLGOP.
The problem is that if he announces an Independent bid, he's going to solidify his reputation as an unprincipled opportunist and lose tons of endorsements and face demands for a return of contributions. His fundraising is going to dry up.
The only people inclined to give him money would be the Teacher's Unions and other Democratic front groups hoping to split the GOP. But the instant they do, nobody in Florida or around the country would believe that his veto of SB6 was the result of anything other than a quid pro quo arrangement.
The other option is for him to do a full Specter and cross over to the Democrats and run for the Senate. But if he does it now, not only does he risk splitting the Democrats, he will do so along racial lines and even more solidify his opportunist reputation, as well as confirm that the SB6 veto was a quid pro quo deal. Worse, he will lose the primary and go on to lose (very very badly) to Rubio if he does somehow prevail over Meek.
But if he drops out and endorses Meek, he earns himself some chits to call in when he makes the switch to the Democrats and decides to run for some other office in the near future - likely a second term in Tallahassee, this time wearing a D.
I predict he loses then as well.
Charlie Crist should be a case study of what happens when a moderate Republican takes the "moderation" too far.