C’mon. We all know it’s coming.

Visibly sad, Snowe called Castle “an outstanding public servant who was committed to the common good of his state and country.”…

At times, as the Maine Republican talked about this issue, she became exasperated.

“Ideological purity at 100 percent is a utopian world and I don’t know who lives in utopia. I’ve never lived in utopia,” said Snowe.

I asked about the argument her GOP colleague Sen. Jim DeMint made to me a day earlier in his office, that Americans no longer want what he called “mushy” lawmakers in the middle.

“What works in South Carolina and Delaware may not work in Maine. We all have different views. We’re independent,” Snowe responded, “I can’t go back to the people of my state and say, excuse me, I have to be one hundred percent ideologically pure because someone has dictated that from another state. It just wouldn’t wash,” she said.

She’s up for reelection in 2012 and no doubt will be tea-party enemy number one next cycle. Here’s her dilemma: Does she stick with the GOP in the expectation that grassroots anti-establishment enthusiasm will diminish once the Republicans are back in power? She’ll be primaried regardless, but as McCain proved, it’s possible for a RINO to survive a challenge from a “true conservative.” Or does she decide that the big push to defeat Obama will keep grassroots enthusiasm sky high in 2012, in which case she’s in mortal peril of going the way of Bob Bennett and Murkowski? If she does jump ship, she’s better off doing it sooner rather than later. The longer she waits, the more it’ll look like she’s acting purely opportunistically, out of fear of losing, than making a stand on principle. The specter of Specter looms large!

An early warning sign, perhaps, from the Anchorage Daily News:

Murkowski said she’d found some support among fellow senators, even if none was openly telling reporters they would back her write-in bid.

“The encouragement is, ‘Do what is right,’ ” Murkowski said colleagues told her. “And that’s ultimately what you look to do. Do what is right for the people that you represent and your state and yourself, your family. If you do what’s right, all is good.”

Sen. Olympia Snowe, R-Maine, a moderate senator, wouldn’t disclose what sort of conversation she had had with Murkowski Thursday, other than to say that “she’s a great colleague and a friend as well.” But Snowe also said Thursday that the Republican Party wouldn’t achieve a majority with the tea party alone. It would also require moderate Republicans like herself, Snowe said, and members “across the range of political philosophy.”

Follow my thinking here. Scott Brown’s also up next cycle and is surely worried about the primary. Collins may already be pondering her chances in 2014. Ben Nelson’s broken with Democrats on all sorts of votes over the past six months to atone to Nebraskans for the Cornhusker Kickback, and Mark Pryor must be nervous about the unholy beating Blanche Lincoln is about to take in Arkansas. And of course, Joe Lieberman’s been a man without a party for four years. Put ’em all together and how’s this for a radical possibility: Now that they’ve got a critical mass, what if the RINOs and DINOs huddle and decide to form … an independent caucus? They could point to the growing power of independents among the electorate, claim that the lesson of this year is that Americans are tired of “politics as usual,” blah blah blah. They could buy some political cover for themselves by insisting that they’ll continue to vote with their respective former parties on most issues, but henceforth they’ll caucus together in the interest of common ground and “solutions” and so forth. For maximum effect, they’d all have to switch together; any one of them peeling off alone would be thought of as treason, but everyone peeling off together is a Movement. And having RINOs join DINOs in defecting and vice versa softens the blow of the betrayal among each side’s base. The Kossacks would go nuts if Ben Nelson split and grassroots righties would go nuts if Scott Brown split, but if they both split together then the balance of power between the parties stays the same and everyone’s a bit more chill.

I assume it won’t happen, partly because it’s unprecedented and partly because splitting means they’ll each have to face three-way crapshoot elections in their home states the next time they’re up. But if they think they’re doomed in the primaries, what do they have to lose? Besides, there’s a slim chance — emphasis on slim — that two more independents will be joining them next year. If the Dems make a deal somehow to back Crist, he can still beat Rubio. And based on what I’m seeing on the wires at the moment, it looks like Murkowski is going ahead with her write-in campaign. Exit question: What if, by scaring off Snowe, Brown, et al., O’Donnell’s win actually costs the GOP control of the Senate? Revenge of the RINOs?

Update: Hmmmmmmmmm.

There’s still room for centrists in the Republican Party, the party’s Senate campaign chief said Friday…

“Absolutely,” Cornyn said when asked if centrists are welcome. “People have to understand that this country is a big, diverse country, and not every region and every state is the same.”

“I think what matters is what the voters in Maine and what the voters in the individual states think about the senator or the candidate,” Cornyn said of how senators such as Susan Collins (R-Maine) might handle the prospect of a Tea Party challenge in 2012.