TALLAHASSEE, Fla. -- Former Florida Gov. Charlie Crist, who was elected the state's chief executive as a Republican and then ran unsuccessfully for the U.S. Senate as an independent, has announced that he's switching to the Democratic Party.

Crist revealed his long-anticipated conversion Friday after more than two years as an independent. He made the announcement on Twitter and included a photo of his new voter registration form that he filled out at the White House.

Crist's party switch reflects the growing concern among some moderate Republicans that their party has left them behind by shifting to the right on a range of issues, including immigration, education and the environment.

"The leadership of the party lately has gone off the cliff, I wasn't comfortable enough," Crist said by telephone while boating off of Miami and before a planned dinner with Democratic Sen. Bob Graham, a former Florida governor. "What I love most about our state is our people ... I just have a feeling in my heart right now is that leadership doesn't appreciate that fact."

Republicans, anticipating the switch, have been attacking Crist for months, running a television ad and scores of press releases pointing out his previous conservative positions as Crist campaigned with President Barack Obama and other Democrats.

"I really feel at home. A lot of it was inspired by what Democrats have stood for, and honestly, friends have told me most of my political life, 'Charlie, you're really a Democrat and you just don't know it," Crist said.

Crist's announcement fanned speculation that he would seek to regain his old job from Republican Gov. Rick Scott in 2014. Scott is a former hospital chain CEO who has struggled with low favourability ratings since taking office.

"I will consider it, and I will think about it," Crist said when asked about a gubernatorial bid.

Earlier Saturday, Republicans gathered for a meeting and said they will be extra motivated to re-elect Scott if his opponent is Crist, who left the Republican Party to become an independent during his unsuccessful 2010 run for the Senate.

"Bring it on," Peter Feaman, the party's national committeeman, told a room of Republican activists. "That man sat at my house, in my kitchen, at my breakfast table and told me he was a Ronald Reagan Republican. OK, I'm putting my boots on, because guess what? You lied to me."

Should Crist run, he could become the first person to serve as Florida governor as a Republican and a Democrat. Crist only served one term before choosing to run for Senate instead of re-election.

Crist was a popular moderate governor and met often with Democratic leaders. He won over many black leaders by championing civil rights issues, prompting one black lawmaker to describe him as the first black governor.

Crist was elected Florida governor in 2006 as a Republican. As he moved to run for the U.S. Senate in 2010, he faced a tough primary challenge from the right and bolted the Republican Party to run as an independent. He lost a three-way Senate contest in 2010 to Republican Marco Rubio.

Crist, 56, spoke at the Democratic National Convention in Charlotte, North Carolina, that nominated Obama for a second term and campaigned for his re-election. Obama ended up narrowly winning Florida.

But it is unlikely that Crist would get a clear path to the Democratic nomination. Former State Sen. Nan Rich has already jumped into the race and former Chief Financial Officer Alex Sink could run. Sink barely lost the 2010 governor's race to Scott. Some Democratic activists will remember the many elections in which they fought Crist, who often called himself a Ronald Reagan Republican.