The former Republican made the announcement in an op-ed piece published in Sunday's Tampa Bay Times. The endorsement came as Republicans are gathering in the Tampa Bay area for the GOP convention. It also came amid preparations statewide for Tropical Storm Isaac.
Crist left the Republican Party during his unsuccessful bid for a US Senate seat in 2010 and is currently registered as having no party affiliation. He was elected governor of Florida as a Republican in 2006.
In the Tampa Bay Times article, Crist wrote he's "confident that President Barack Obama is the right leader for our state and the nation."
GOP Chairman Lenny Curry says Crist's "political ambition will always come before the needs of Floridians."