Has Rubio been bitten by the Establishment Vampire?

Florida Senator Marco Rubio has been a Tea Party favorite, much like South Carolina Governor Nikki Haley was. Haley endorsed Romney and was thoroughly rebuked by her state's voters when Gingrich won going away.

Rubio hasn't officially endorsed Romney but he has come about as close as Sarah Palin has to endorsing Gingrich. In fact, Rubio's rebuke of Gingrich's ad that went after Romney for being anti-Immigration may have been almost as effective in deflating the Newtmentum in Florida as Romney's negative and egregious ads that targeted Gingrich. The Senator from Florida even rebuked Gingrich when the former Speaker likened Romney to Crist. Rubio defended Romney as someone who stood by him in his race against Crist.

As John Hawkins points out at Right Wing News, Romney didn't get behind Rubio until the Tea Party had spent a year pushing Rubio past Crist:

Back in May of 2009, I got together with Erick Erickson, Stacy McCain, and other bloggers to support Marco Rubio and went after the National Republican Senatorial Committee for endorsing Charlie Crist over Marco Rubio.... 

Back then, when Charlie Crist had what looked like an overwhelming lead and the support of the GOP establishment, guys like Mitt Romney were absolutely nowhere to be found. 

Of course, Mitt did eventually BOLDLY endorse Marco Rubio. It was almost a YEAR later on April 17 of 2010 and the GOP primary was already as good as over.

So why is Rubio siding with the establishment in this Florida primary? What has happened to these Tea Party favorites who wouldn't be sniffing higher public office if not for the conservatives who fought for them?

I can think of only two possibilities. Either Rubio got bit by an establishment vampire or it's nothing more than the disgraceful human tendency to betray instead of doing what's right.