The biggest Florida speaker at the Democratic National Convention wasn’t a Democrat.

Yet.

After former Republican Gov. Charlie Crist’s speech Thursday night, it’s only a matter of time before he officially joins the party’s ranks in a slow march to running for governor in two years.

Crist’s high-profile role disturbed many Florida delegates, but it furthered President Obama’s campaign message — that the Republican Party is too extreme.

“As a former lifelong Republican, it pains me to tell you that today’s Republicans — and their standard-bearers, Mitt Romney and Paul Ryan — just aren’t up to the task,” Crist said. “They’re beholden to ‘my way or the highway’ bullies, indebted to billionaires who bankroll ads and allergic to the very idea of compromise.”

Crist’s speech was as much a condemnation of today’s Republican Party as it was an explanation of why he’s officially moving toward the Democratic Party and away from the conservative positions he once espoused.

Republicans and many Democrats alike won’t let Crist forget he campaigned for years as a pro-life, anti-gay marriage, gun-touting “Reagan Republican” and “Jeb Bush Republican.” In 2010, in his unsuccessful Senate bid, he bashed Obama’s agenda and ran as a “true conservative.”

“Is he here, and in this for his principles?” asked Democratic delegate Bob Hartnett of Orlando. “I’ve got a long time to think about that. But there are many others in this party qualified to lead and be onstage representing our people.”

Crist said Thursday that he was addressing the convention “not as a Republican, not as a Democrat, but as an optimist.” Crist referred to Bush in his speech as “my friend” — a comment sure to irk conservatives as well as Bush, who has described Crist as an opportunist.

Crist ran as a conservative in his first statewide race in 1998, when he unsuccessfully ran for U.S. Senate. With Bush’s help, Crist was elected education commissioner, attorney general and, in 2006, governor where he governed as a centrist.

“Half a century ago, Ronald Reagan, the man whose relentless optimism inspired me to enter politics, famously said that he didn’t leave the Democratic Party; the party left him,” Crist said. “I can certainly relate. I didn’t leave the Republican Party; it left me.”

But the timing of Crist’s departure from the Republican Party suggests a colder political calculation. He officially left the party just before a candidate-qualifying deadline in the 2010 Senate race.

Crist was running against fellow Republican Marco Rubio, and Crist would have handily lost the GOP primary. So he left the GOP and ran as an independent, though he ultimately lost the general election.

Crist’s undoing in the GOP: The infamous “hug,” his decision to appear onstage with Obama in 2009 in Fort Myers, where he literally embraced the president and the $787 billion stimulus program.

“That hug caused me more grief from my former party than you can ever imagine,” Crist said. “But even as the Republican Party fought tooth and nail to stop him, this president showed his courage, invested in America — and saved Florida.”

Crist was the only Republican governor to break ranks with his party to talk up the stimulus, which every GOP governor and Legislature wound up using to patch holes in their budget.

As the primary race intensified, Crist then flip-flopped on the stimulus, alternately bashing it and talking it up depending on the day or the media outlet he was addressing. Crist released a radio ad that bashed Obama for spending. The Florida Democratic Party later released a TV spot that questioned Crist’s authenticity.

Crist brushed aside those differences Thursday night.

“I’ll be honest with you, I don’t agree with President Obama about everything.,” Crist said. “But I’ve gotten to know him, I’ve worked with him, and the choice is crystal clear.”

Crist credited Obama with not only saving the economy in Florida, but for fighting to ensure that BP cleaned up the Gulf Coast after the oil spill. Crist said nothing Thursday about the president’s Affordable Care Act, which Crist once described as scary.

Crist’s role at the Democratic National Convention underscores the weakness of the party in Florida, where only Sen. Bill Nelson holds a statewide seat. The Legislature is overwhelmingly Republican, even though registered Democrats outnumber Republicans in the state.

Democrats want a winner. They note that, as an independent, he garnered 1.6 million votes in 2010 to Rubio’s 2.6 million. Democratic Rep. Kendrick Meek came in third, with just over 1 million votes, the overwhelming majority of which would likely have gone to Crist had there not been a three-way race.

Meek won’t rule out running for governor against Crist. Florida Senate Democratic leader Nan Rich, of Weston, is running. And former state Chief Financial Officer Alex Sink might want a rematch against Republican Gov. Rick Scott, who narrowly beat her in 2010.

“If by some miracle Charlie Crist makes it out of the gauntlet of a Democratic primary even though he called himself a staunch conservative, he then has to run on his dismal record,” said Scott’s political advisor and pollster Tony Fabrizio, who ticked off the dismal economic indicators that unfolded on Crist’s watch.

Former Miami Beach Democratic state Sen. Dan Gelber recently penned a column welcoming Crist to the party, and he chuckled at Republicans painting the former governor out as a flip flopper.

“Just a week ago,” Gelber said, “Republicans nominated Mitt Romney, a former pro-choice, pro-gay marriage, anti-Reagan economic, self-described progressive who used to be concerned about global warming.”

Crist steered clear of mentioning Romney’s reversals, but he did echo the Democratic talking point that the Republicans “would break the fundamental promise of Medicare and Social Security” — a line of attack that could prove devastating in must-win Florida, a state with a disproportionate share of elderly residents.

Crist’s speech was brief. Accustomed to having a fan at his side to keep cool, Crist didn’t have the luxury on Thursday night and was on the cusp of breaking into a sweat on stage.

But he ended quickly and smoothly as he started to win the home crowd, noting “I used to play quarterback just down the road from here at Wake Forest University. My dad always told me, ‘Charlie, it takes a cool head to win a hot game.’”

Crist said Obama had the “cool head” the nation needs.

"That's the leader Florida needs. That's the leader America needs," he said, as the crowd rose to its feet. "And that's the reason I'm here tonight."