Charlie Crist used to be a Republican. Then he was an Independent. On Monday, he announced his Democratic candidacy for governor of Florida. So how did we get here? (The Washington Post)

Former Republican Gov. Charlie Crist presented himself to Florida voters on Monday as a Democrat.

And while Republicans launched an immediate ad campaign portraying him as an opportunistic shape-shifter, Crist made clear he intends to try to use his very willingness to adopt a new identity as a political advantage in itself – setting him apart from government dysfunction and polarization that polls show Americans detest.

“The far right wing seems to want to make much of my party affiliation,” Crist told cheering supporters and family, including his Republican parents, gathered for the Tuesday announcement in his hometown of St. Petersburg. “That is precisely what’s wrong with politics today.”

“No matter what they say, it’s not a sin to reach across the aisle,” Crist said. “It’s your obligation to work together. So yes, yeah, I’m running as a Democrat. And I am proud to do it. But to every independent and every Republican, like Mom and Dad, who feels we are losing our way, please join us.”

The scene was as much a statement of the Democrats’ eagerness to mount a serious challenge to Republican Gov. Rick Scott in November 2014 election as it was a culmination of Crist’s three-year-long evolution away from the GOP.

Florida’s Democratic establishment has welcomed Crist not just as a new friend but as a presumptive standard-bearer.

His new campaign is being advised by President Obama’s 2008 Florida director. On Monday, Crist was joined on stage and enthusiastically endorsed by some of the state’s most prominent Democrats, including former state Attorney General Bob Butterworth, U.S. Rep. Kathy Castor of Tampa and former state House Democratic leader Dan Gelber.

Florida Democrats are desperate for a winner because they have lost their previous four attempts at the governor’s mansion – including in 2006 to Crist. They have essentially no power in Tallahassee. With Crist, a relatively popular figure, the Democrats begin their race with tens of millions of dollars’ worth of image-making already in the bag.

“It’s very expensive to run in Florida,” said Gelber. “Very few people in Florida have any identity other than major sports figures and a precious few elected officials. He is one of the handful that does. And it’s a very positive one.”

Crist and his supporters point to a number of key moments that help him stake his claim as a legitimate Democrat. Among them: His move in 2008 to keep crowded voting locations, many of them heavily African-American with large turnout in favor of Obama, open late to permit everyone to cast their ballots; his support for restoration of felons’ voting rights; his support for Obama’s stimulus, which Crist referenced indirectly Monday as his support for helping thousands of teachers avoid layoffs; and his veto of a GOP-backed teacher tenure bill.

“He was a very nonpartisan guy,” Gelber said. “He governed as a non-partisan and as a social moderate. And a lot of us Democrats who served with him really liked him.”

Crist first abandoned the Republican Party under duress in 2010 when it was clear he would soundly lose the GOP nomination for U.S. Senate to Marco Rubio. He switched to run as an independent, but lost anyway. Rubio and his tea-party supporters blasted Crist for welcoming Obama’s stimulus dollars and, at one point, hugging the Democratic president.

Crist became a Democrat in 2012 – and over the past year he has meticulously courted top Democratic donors and activists in anticipation of a second political act. Obama gave him a speaking slot at the party’s national convention in Charlotte, and Crist devoted much time that week to socializing with top Obama bundlers and supporters.

Crist faces a challenge for the Democratic nomination from a former state senator, Nan Rich, who has watched with dismay as her longtime allies have tried to ease her out of the race to make way for Crist.

“It’s because of the relationship that he developed with Obama,” Rich said in an interview Tuesday. “There’s kind of a circle there that has been supportive of him or supportive of this idea, because they inaccurately and mistakenly believe that Charlie is the only one who can beat Rick Scott.”

Scott’s political organization, called Let’s Get to Work, launched an ad campaign Monday citing past quotes from Democrats attacking Crist as a flip-flopper. Strategists believe Scott’s campaign could cost as much as $100 million – and it appears that much will be spent attacking Crist from the get-go.

State GOP Chairman Lenny Curry said Monday Republicans will criticize Crist for deciding, after one term, to run for Senate instead of reelection at a time that the state was experiencing an economic meltdown.

“He’s just not a serious person,” Curry said.