He’s not saying he’ll support them, mind you, just that he won’t oppose them. Or at least, not publicly. Alternate headline: “DeMint’s opposition to GOP incumbents to be behind-the-scenes only”?

Actually, we already knew that he was leaning this way, but now he’s gone and made it official.

South Carolina Sen. Jim DeMint is privately reassuring his Republican colleagues up for reelection that he won’t recruit or endorse any primary opponent against them, vowing to raise more than $10 million aimed mainly at taking down Democratic incumbents.

In a letter obtained by POLITICO, the tea party favorite appears to be taking steps to soothe post-election tensions with his GOP colleagues, including some who say his political tactics have been counterproductive…

“First, despite rumors to the contrary, I want to assure you that I will not recruit or support primary challengers to incumbent Republicans, and you can also be assured I will support all of our Republican nominees for the Senate,” he wrote in the letter he sent Wednesday. “My goal for 2012 is to raise more than $10 million through the Senate Conservatives Fund to replace incumbent Democrats with conservative Republicans.”…

In an interview last month with POLITICO, DeMint said his “plan right now is to support all our incumbents” in 2012. But in Wednesday’s letter, DeMint stops short of saying he’ll support all GOP incumbents. And in a follow-up interview Thursday, he said he’s not promising support for GOP senators in primaries – only that he’ll stay out of the primaries altogether.

The Democrats at the top of his list are Tester, Conrad, Ben Nelson, and Joe Manchin. I’m mighty curious to see how he’d react if either of those last two switched to the GOP before the 2012 campaign started gearing up. Anyway, a serious question: Why would DeMint agree to support the GOP nominee in all cases? The crux of the “true conservative”/RINO debate before the Delaware primary was whether he was right when he famously said we’re better off with a Senate caucus of 30 Marco Rubios than 60 Arlen Specters. Better that Chris Coons win the seat than Mike Castle, in other words, because Castle won’t stand for conservative principles on every occasion and that’ll end up damaging the Republican brand. If conservative principle means we have to suffer in the minority for one term or two terms or 20 terms, so be it; eventually the public will tire of liberal government and will embrace the conservative Republican alternative. That was the argument from O’Donnell supporters, in any event.

Does that logic … no longer apply? Better to have 60 Olympia Snowes in the Senate than a 70/30 Democratic majority? That must be the new rule, because as our Greenroom contributor Karl pointed out to me recently, that letter from DeMint fans threatening Republicans who criticize him makes no sense otherwise. Their big complaint was that people were blaming DeMint for having ruined the GOP’s chances at a Senate majority. But, per DeMint’s own “better 30 Rubios than 60 Specters” logic, the majority is worth sacrificing. Better to lose with Ken Buck and Christine O’Donnell than win with Jane Norton and Castle — that’s the DeMint philosophy in a nutshell, at least until recently. Why are his supporters angry at people for suggesting that he’s willing to sacrifice GOP seats in the name of principle when he’s all but said that before himself?

If you read the whole Politico piece linked up top, you’ll see that he’s also vowing that this will be his last Senate term. I wonder if he’s planning to retire or to pursue … another office. Exit question: Is his new “no incumbent challenges” rule an early sign of the tea party going mainstream? Hmmmmmm.