Arlen Specter's switch is the first sign of a real and lasting division between "moderate" Republicans and the conservative movement that elected them and gave them power for a generation.

These "moderate" Republicans are not liberals. Most call themselves "conservatives." Their ranks include Specter, Olympia Snowe, Richard Lugar, Arnold Schwarzenegger. Their spokesmen include David Brooks, David Frum, Daniel Larison, and Michael Smerconish.

They are rich, country club Republicans who like being the Upper Class. They live in wealthy suburbs (or posh urban neighborhoods) to be as far from "the rabble" as they can and to send their kids to mostly-white schools. They support the largest prison establishment in the world for the working class but oppose any form of accountability for Wall Street and Washington. They support imperial wars as long as Other People's Children fight and die.

They supported Richard Nixon, even through Watergate, and Gerald Ford too. They supported Ronald Reagan, even through Iran-Contra. They supported good ol' George and his boy George W, even through Iraq and Katrina.

But they couldn't support Sarah Palin because she was just too ignorant - and defiantly proud of it. They couldn't support Mike Huckabee because he's a fast-talking southern Baptist preacher.

Right now they're having a profound identity crisis. They like Barack Obama because he's smart and flexible - and willing to plant himself firmly between the anti-corporate Pitchforks and the CEO's. They don't like the Teabaggers or their champions - Newt Gingrich, Tom DeLay, Dick Armey, Rush Limbaugh, Glenn Beck, Sean Hannity, Bill O'Reilly.

Pundits like David Frum have the luxury of critiquing this division.

Let’s take this moment to nail some colors to the mast. I submit it is better for conservatives to have 60% sway within a majority party than to have 100% control of a minority party. And until and unless there is an honored place made in the Republican party for people who think like Arlen Specter, we will remain a minority party.

But Republicans who are up for election don't have the luxury of waiting for a conservative-moderate "deal." Because the 2010 campaign is underway, Arlen Specter had to make a choice - whether to stand with the Teabaggers or Obama. As he said this morning, he was not going to let his long career be decided by the Republican primary electorate - the Teabaggers.

It's not clear if other Republican Senators will follow Specter across the aisle. Neither Olympia Snowe, Susan Collins, nor Richard Lugar are up in 2010. Judd Gregg and Mel Martinez are retiring. That leaves George Voinovich (OH), Charles Grassley (IA), and Lisa Murkowski (AK).

But it doesn't really matter. The Republican Party will keep shrinking as long as conservatives like Sen. Jim DeMint (SC) insist on ideological purity:

“I would rather have 30 Republicans in the Senate who really believe in principles of limited government, free markets, free people, than to have 60 that don’t have a set of beliefs.”

And he may get his wish because Republicans will losing key elections as long as Barack Obama is President and the Teabaggers go nuts - alienating all remaining Republican moderates.