Well it's not as if Clinton has ever exhibited principle or anything

So, Bill Clinton tried to get Kendrick to drop out of the Senate race here and endorse Charlie Crist.  I can understand why Clinton would prefer Crist-snakes in the grass slither together, but but it was a smarmy move even by Clinton's incredibly low standards.  The obligatory crappy quote:

“Not being seen as a quitter was more important than stopping someone who was so opposed to what you and your party had stood for,” said one Democrat who had been hoping to close the deal.

An alternate explanation is that Meek wasn't worried about being seen as a "quitter", he simply couldn't stomach the thought of endorsing Charlie Crist.  After all, he may not like Rubio's stand on the issues but Meek is smart enough to know that Crist's "stands" belong to the highest bidder. 
 
Meek is displaying principal.  For Mr. Clinton's benefit:
 

Principle prin·ci·ple [prínssəp'l]

ethical standard: a standard of moral or ethical decision-making