WHEN CRIST EXITS STAGE LEFT…. Florida Gov. Charlie Crist was effectively given a choice: get humiliated in a Republican Senate primary or run as an independent and improve his odds of having a job in January. Not surprisingly, he’s going with the latter.

Gov. Charlie Crist, a pariah in the Republican Party that has been vital to his success, will launch a risky political career Thursday as a “people’s candidate” for the U.S. Senate with no party affiliation.

Crist began telling campaign donors of his decision Wednesday, which he will announce at 5 p.m. at Straub Park in downtown St. Petersburg, surrounded by family members, friends, local supporters and an army of media personnel. It will be an extraordinary event in Florida’s colorful political history, as a one-term governor who blew a 30-point lead in the Republican Senate primary is forced to run an unconventional race.

“I think the people are concerned about the future, and they’re interested in having people who put them first, instead of politics,” Crist said. “I think that’s where they are.”

There are plenty of interesting angles to all of this — how will Crist fare, will he have any money, why Florida is so odd — but from a national perspective, the key takeaway continues to be the effort to drive moderates away from the Republican Party.

Democratic National Committee Chairman Tim Kaine said yesterday that the Republican Party is “kind of throwing [Crist] out,” and making all moderates “feel like they don’t have a home” in the party.

In this case, the analysis is more than just election-year rhetoric. The “purge” has been underway for a while now, it’s making the Republican Party smaller, more rigid, less reasonable, and far less open to diversity of thought. Crist, apparently, no longer feels welcome in the GOP. Neither did Arlen Specter. Dede Scozzafava was forced out. Utah Sen. Bob Bennett’s (R) career is ending because his conservatism wasn’t extreme enough for the party base.

It’s possible that the electoral consequences of this will be limited. Under normal circumstances, a party that deliberately moves away from the American mainstream scares voters away. Republicans have all but posted a sign on the door at RNC HQ that reads, “He-Men Moderates-Hating Club,” which would ordinarily send the electorate running in the opposite direction.

But that’s what makes this year’s landscape so disconcerting — Republicans are only rolling out the welcome mat for hard-right ideologues, but because voters are frustrated with the recession and congressional dysfunction, the GOP is likely to make gains anyway.

That is, unless the economy starts to recover faster, and Democrats are able to demonstrate that a GOP that’s even too far to the right for life-long Republicans doesn’t deserve mainstream support.

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Steve Benen

Follow Steve on Twitter @stevebenen. Steve Benen is a producer at MSNBC's The Rachel Maddow Show. He was the principal contributor to the Washington Monthly's Political Animal blog from August 2008 until January 2012.