This is pretty big news that shows the institutional power of the tea party conservative base. In the wake of last night’s disaster in NY-23, John Cornyn, the head of the National Republican Senatorial Committee, the GOP campaign arm for Senate races, announced that his organization will not endorse or spend money in “contested primaries.”

“We will not spend money in a contested primary,” Sen. John Cornyn, the chairman of the National Republican Senatorial Committee, told ABC News in a telephone interview today.

“There’s no incentive for us to weigh in,” said Cornyn, R-Texas. “We have to look at our resources. . . . We’re not going to throw money into a [primary] race leading up to the election.”

Cornyn said his pledge extends to races for open Senate seats — not incumbents who may face primaries next year. The NRSC so far has endorsed candidates in four open Senate seats — Florida, Missouri, Illinois, and Pennsylvania.

If this were happening in the Democratic Party, I would praise it, so let me briefly do the same here. People on the ground should decide who they want to be their nominee, not Senators playing favorites from back in Washington. Committees like this should respect their base and allow them to pick the candidates, and primaries are generally healthy events for parties. I certainly wish Rahm Emanuel heeded this.

But this does show the real fear out there in the GOP establishment of angering their base. I’ve already documented how Carly Fiorina and Charlie Crist have been targeted by conservatives for defeat in favor of their preferred candidates, despite establishment backing. Cornyn is basically kowtowing to that dynamic, and so are the candidates themselves, according to the story:

Asked what endorsements mean, then, Cornyn said some candidates may want the backing to help line up support and financing. Beyond that, however, he said NRSC endorsements won’t mean very much in practice.

“Endorsements, frankly, are overrated…. They can to some extent be a negative,” Cornyn said, noting that candidates in New Hampshire, California, and Colorado, for example, have asked the national party to stay out of their races.

Wow. GOP candidates for the US Senate cannot have the liability of the NRSC working for them. That’s pretty astonishing.