According to the Tampa Bay Times:
It was just a matter of time. Charlie Crist is becoming a Democrat.
Crist — Florida’s former Republican governor who relished the tough-on-crime nickname "Chain Gang Charlie" and used to describe himself variously as a "Ronald Reagan Republican" and a "Jeb Bush Republican" — on Friday evening signed papers changing his party from independent to Democrat.
He did so during a Christmas reception at the White House, where President Barack Obama greeted the news with a fist bump for the man who had a higher profile campaigning for Obama’s re-election this year than any Florida Democrat.
As reported below is the tweet he sent out.
Proud and honored to join the Democratic Party in the home of President @barackobama! twitter.com/charliecristfl…
— Charlie Crist (@charliecristfl) December 8, 2012