President Obama responded with a fist bump after Crist signed the papers, the Tampa Bay Times reported. Crist, an independent for more than two years, endorsed the president in this year's election over his Republican challenger, Mitt Romney.
"I've had friends for years tell me, 'You know Charlie, you're a Democrat and you don't know it,'" Crist told the newspaper.
Crist served in the state Legislature before winning the governorship in 2006. Trailing Marco Rubio in a Republican primary for the U.S. Senate, Crist became an independent in 2010. He ran behind Rubio and ahead of the Democratic candidate in the general election.
The Times said Crist is believed to be considering another run for governor in 2014. He would be likely to have competition in the Democratic primary.
Florida has been split between the two parties in recent years. Obama carried the state narrowly in November, Gov. Rick Scott and Rubio are both conservative Republicans while Democratic Sen. Bill Nelson won a third term this year with 55 percent of the vote.