The National Republican Senate Committee has put its foot down, according to NBC News: No longer will it sit out party primaries. Why it thinks this will make a big difference isn't clear.

The Republican Party, by most accounting, should all-but-control the Senate already. But in 2010, far-right conservatives displaced more moderate candidates in Senate races in Nevada and Delaware; in 2012, it happened in Indiana and Missouri. It almost happened in Alaska in 2010, but the sitting Republican ran as independent to keep her seat. That swing of four votes would give the body a 49-49 vote split, with two independents that vote with the Democrats. Not quite there, but better than where the party is now, reliant on filibusters to block any- and everything that the Democrats advance.

The NRSC would prefer this not happen again. NBC News:

"Would we spend money in a primary? Yes, we would if that’s the right move at the time," Rob Collins, executive director of the National Republican Senatorial Committee, told reporters Tuesday. "The path to getting a general-election candidate who can win is the only thing we care about." …

"I can do whatever I want," Collins said, "and I’m going to do whatever I need to do to win."

Sure, that makes sense, in general. Collins' problem, though, is that the NRSC dropping money in a primary is hardly a guarantee that it will end up with the candidate it wants.

The threat, as NBC News points out, is organized opposition in the form of the Senate Conservatives Fund, an organization founded by former-senator-and-now-Heritage-Foundation-chief Jim DeMint that still largely adheres to DeMint's far-right political priorities. The threat posed by the SCF to the NRSC, the party's official Senate committee, is severe enough that rogue Sen. Ted Cruz needed to swear off any involvement with the group in order to make nice with his peers in the chamber.

Among others, the SCF has committed to support challengers to Senate Minority Leader Mitch McConnell and Mississippi's Thad Cochran — though that latter endorsement may have been a little a bit hasty. As The New York Times' Jonathan Martin reported earlier this month, the GOP establishment has been putting pressure on those working with the SCF in an attempt to freeze them out. "[A] senior official at the [NRSC] called individual Republican Senate campaigns and other party organizations this week and urged them not to hire the firm, Jamestown Associates," Martin wrote, "in an effort to punish them for working for the Senate Conservatives Fund."

But the primary losses in 2010 and 2012 obviously pre-date the SCF. The Senate Conservatives Fund may be the well-funded and aggressive embodiment of the conservative push that elected Christine O'Donnell, Sharron Angle, Richard Mourdock, Todd Akin, and Joe Miller, but it's not why all five of them won their elections. They won on the basis of their own campaigns and by running hard-right campaigns in primaries looking for hard-right candidates. In every case but Miller's, they won by more than 5 percentage points — a wide margin.

Mourdock, in Indiana, won by over 20 points, and he would not have lost even if his opponent had the support of the NRSC. When he went to talk to the group before he won his primary, he says that the response he got was, "What are you doing here? You know we help incumbents." Which the NRSC almost certainly did in each of these five races, doing everything shy of endorsing. Arm-twisting ad firms wasn't invented in 2013.

In fact, the stamp of approval from the establishment that NRSC investment would convey might prove to be more a liability than anything. We pointed out how the establishment / insurgent dynamic is playing out in a race in Alabama on Tuesday. If the far-right insurgent wins in that primary run-off — in the face of institutional Republicanism descrying his candidacy — there's not much reason to think that the party machine will be able to sway primary races elsewhere.

The Republican institutional strategy for containing Tea Party-ism started with an attempt to wait it out. Then it was to bargain, offering some wins (like the shut down). Now, it realizes that it needs to fight back. It's not yet clear the establishment can win.

Photo: Images from the AP. Clockwise from top left: Akin, O'Donnell, Mourdock, Angle.