In what had become one of the worst-kept secrets in Florida, Gov. Charlie Crist announced Thursday that he is abandoning the Republican Party primary to pursue a U.S. Senate seat as an independent.

Speaking to a crowd of supporters in St. Petersburg late Thursday afternoon, Crist  took aim at the partisanship on Capitol Hill.

"Our political system is broken. People are fed up with the gridlock," he said.

As a man without a party, Crist acknowledged he was entering "uncharted territory" with an independent run for Senate.

"The easy thing would have been for me to run for re-election as governor. But it's never been about doing what's easy for me," Crist said.

"We're going to take it straight to November. It's not one's club decision or the other. It's your decision to make.

"I need you, the people, more than ever," he told the cheering crowd.

By shifting to no-party status, Crist acknowledged months of political polls that have shown him trailing former House speaker Marco Rubio by 20-plus points in the Aug. 24 GOP primary.

Opinion polls have shown Crist far more competitive as an unaligned candidate in a three-way general election contest with Rubio and likely Democratic nominee Kendrick Meek.

“Gov. Crist still doesn’t get it," Rubio said after Crist's announcement. "This race is not about conservative vs. moderate, Republican vs. Democrat or, now, Republican vs. Democrat vs. Non-Party Affiliated," Rubio said. "This election’s outcome was never going to hinge on whether he chose to run as a Republican."

After Crist declared himself an independent, Meek, a congressman from Miami, told CNN's Wolf Blitzer he is "absolutely" looking forward to President Barack Obama coming to Florida to campaign for him.

"I'm all in," he said of his Senate bid. "I'm giving up a safe congressional seat that my mother held."

"I can go into the White House and first-hand speak for Floridians," Meek said.

Crist, a moderate who has increasingly alienated Republicans roiled by Tea Party activists, incensed GOP legislative leaders this month when he vetoed an education reform measure, Senate Bill 6, authored by Republican Party Chairman Sen. John Thrasher, R-Jacksonville.

But while Crist was applauded by teachers and others opposed to SB 6, his claim to independent voters and Democrats is far from assured, political observers say.

The financial and logistical hurdles of running a campaign outside party channels -- and Florida's historical aversion to candidates who go that route -- could prove insurmountable, they say.

Mike Connolly, spokesman for the Washington, D.C.-based Club for Growth, whose early support for Rubio helped transform the former speaker's campaign from a long-shot quest into a fundraising powerhouse commanding double-digit leads in the polls, was quoted as saying:

"I wouldn't say that anybody's winning today. Nobody's gloating. But whatever the polls are today, that's as high as Charlie Crist will go.

"This isn't a situation like Sen. Arlen Specter's, D-Pa., where he can go to the fundraising base of the left -- the unions and so on -- to make up what he's lost. This is the high-water mark of the Crist campaign. It's all downhill from here."

Crist's strategy of peeling off Democratic votes runs against historical tides. Since 1998 no Democratic candidate for statewide office has won less than 78 percent of Florida's Democratic voters, according to a Pollster.com analysis.

Most polls show Crist winning roughly a third of self-declared independents. Even if he were to raise that share to half of those voters -- a very rosy scenario -- he still maxes out at around 35 percent of the electorate, Pollster.com said.

Al Cardenas, a former state GOP chairman and Crist supporter, who now would back Rubio in a three-way race, said he thought Crist would win less than 20 percent of the vote as a party-less candidate.

"He won't have the infrastructure around the state that he would have as a Republican," Cardenas said. "He will have absolutely no ground operation to count on."