I forget sometimes that posts about Beltway infighting can be a bit too inside-baseball for people who follow politics casually, so let’s get everyone on the same page. The NRSC is, as almost everyone knows, the main GOP committee responsible for getting Republicans elected to the Senate. In theory it’s concerned only with helping GOP nominees beat Democrats in the general election but in practice it’s regarded as an incumbent/establishment protection outfit. The most notorious example I can think of offhand is when the NRSC endorsed, ahem, Charlie Crist over Marco Rubio early in the 2010 Florida primary campaign. The Senate Conservatives Fund is the PAC founded by Jim DeMint that helped spearhead the “defund ObamaCare” effort last month. It’s dedicated to electing “true conservative”/tea party candidates to Congress, even if that means primarying Republican D.C. mainstays. In fact, they’ve already endorsed Mitch McConnell’s primary challenger in Kentucky. Under pressure to swear off the group, Ted Cruz reportedly promised his GOP Senate colleagues this week that, although he’s a favorite of the SCF and worked with them on “defund,” he won’t help them fundraise to defeat Republican incumbents.

In other words, you’ve got the most influential GOP establishment fundraising arm declaring war on the most influential grassroots tea-party fundraising arm, which has already declared war on the establishment. It’s an unusually visible expression of the tension that’s been building all year between grassroots righties on the one hand and centrists and business interests on the other. “Defund” and the shutdown are what finally brought it way out into the open, and a bunch of major players in the Senate, including/especially McConnell, Cruz, Rand Paul, and Mike Lee, are caught in the middle.

Can this coalition be saved?

In a warning shot to outside conservative groups, the National Republican Senatorial Committee this week informed a prominent Republican advertising firm that it would not receive any contracts with the campaign committee because of its work with a group that targets incumbent Senate Republicans.

Even more striking, a senior official at the committee called individual Republican Senate campaigns and other party organizations this week and urged them not to hire the firm, Jamestown Associates, in an effort to punish them for working for the Senate Conservatives Fund, a group founded by Jim DeMint, then a South Carolina senator, that is trying to unseat Senator Mitch McConnell of Kentucky, the Republican leader, and some other incumbents up for re-election next year whom it finds insufficiently conservative…

“This is happening because Mitch McConnell is having a complete meltdown,” said Matt Hoskins, executive director of the conservative group. “He can’t defend his record so he’s threatening and attacking everyone who disagrees with him. He’s so rattled, he has decided to declare war on the entire conservative movement, which represents the very people he needs to win re-election. This isn’t the behavior of a confident person. It’s the irrational reaction of a power-hungry bully who isn’t getting his way.”…

“S.C.F. has been wandering around the country destroying the Republican Party like a drunk who tears up every bar they walk into,” said Josh Holmes, Mr. McConnell’s chief of staff, now detailed to the National Republican Senatorial Committee through the election. “The difference this cycle is that they strolled into Mitch McConnell’s bar and he doesn’t throw you out, he locks the door.”

In other words, it’s a secondary boycott of Jamestown Associates aimed at scaring people away from working with the SCF, replete with phone calls to GOP candidates to urge the boycott on them too. And when I say it’s “unusually visible,” I mean it: Check out NRSC strategist Brad Dayspring’s Twitter feed this afternoon. Yowza.

The strategy, obviously, is to crush the SCF by starving them of donors. Republican candidates and big-money establishment donors are essentially being told by the NRSC that it’s “us or them.” If you’re someone who craves influence on the Hill, choosing the tea-party group over the group that backs the Senate minority leader (who might well be majority leader next year) is … risky. Meanwhile, the message to grassroots small-money donors is that giving money to the SCF is kinda sorta like giving it to Democrats because, in some cases, the group is working against the most “electable” Republican in the primary. On the one hand, that’s a shrewd play; “purity” is the SCF’s biggest asset, so framing them as a liberal stalking horse will damage them if the idea catches on. On the other hand, this is the same group that once thought Crist was more electable than Rubio. Either way, the NRSC is now forcing people, including consultant firms, to take sides between the two. This seems unhelpful to party unity in the midst of a big ObamaCare meltdown, but the answer to that, I guess, is that primarying incumbents like Mitch McConnell is “unhelpful” in some ways too. A noteworthy development in the “GOP civil war” chronicles, regardless. Let the RINO/tea party battle be joined.

Odds of all this sturm and drang resulting in a permanent Republican schism and a third party: 30 percent, I’d guess, up from 20 a week ago. Exit question: Do RINO consultant firms get blacklisted too? Ask Liz Mair.