Former Florida Gov. Charlie Crist is officially a candidate for governor again, but this time he is running as a Democrat.

At 3:50 p.m. on Friday, the Florida Division of Elections officially accepted Crist’s paperwork to create his campaign account, setting up what many expect to be one of the hottest governor’s races in the nation.

Crist’s entry into the race is hardly a surprise, with speculation mounting since he campaigned for President Barack Obama’s re-election last year and registered as a Democrat in December 2012. Republican Party of Florida officials have been attacking him nearly daily in anticipation his candidacy.

He spent most of last weekend in Orlando building support with his new party at the Florida Democratic Convention. Crist met with top party officials and Democratic activists, trying to convince them his views now align with theirs.

Crist is challenging Gov. Rick Scott, the Republican who replaced him when he left to run for the U.S. Senate in 2010, losing as an independent to Republican Marco Rubio.

Crist, then a Republican, was elected governor in 2006.

In campaigning on behalf of Obama in Florida Crist declared the Republican Party had become too extreme.

“The party left me,” Crist said in an interview in Orlando last week when asked why he changed his party affiliation.

Crist was not available for comment on Friday. He has scheduled a formal campaign kickoff event on Monday morning in his hometown of St. Petersburg.

In taking on Scott, Crist is challenging one of the least popular governors in the nation. Scott won the governor’s mansion in 2010 by the narrowest margin in Florida history over Democrat Alex Sink.

Though the state’s unemployment numbers have been dropping through most of his tenure, Scott has struggled to regain his footing with voters since his first year in office, when he killed a federally funded high speed rail project connecting Tampa and Orlando, cut state education funding and backed a plan to tie teacher salaries more to standardized test scores of their students.

Republicans continued their criticism of Crist following his filing Friday.

“Charlie Crist has now officially filed to run for the position he once abandoned,” RPOF chairman Lenny Curry said in a statement.

Former State Sen. Nan Rich, a Democrat, has also filed to run.