Last week, Greg Brannon failed to force a runoff in the North Carolina Republican primary for U.S. Senate. Polls show Paul Broun fading to third or fourth place in Georgia’s primary later this month. Nobody seems to have laid a glove on Lindsey Graham in South Carolina, whose primary will be held in June.

Senate Minority Leader Mitch McConnell was panned by conservatives for the prediction he made to the New York Times about Tea Party primary challengers. “I think we are going to crush them everywhere,” he said. “I don’t think they are going to have a single nominee anywhere in the country.”

A provocative way for a Republican leader, locked in a tough race himself, to talk about the most passionate activists in his party. But aside from an open seat in Nebraska, where Ben Sasse appears to hold a double-digit lead, is McConnell wrong?

Tea Party candidates still have an outside chance of toppling Thad Cochran in Mississippi and winning the nomination for the Senate seat being vacated by Tom Coburn in Oklahoma. They don’t yet reliably lead in either of these races, however. And from the challenge to Pat Roberts in Kansas to McConnell in Kentucky, conservative insurgents are way behind.

All this is a big change from when Rand Paul beat Trey Grayson, Marco Rubio and Pat Toomey would have pasted Charlie Crist and Arlen Specter, respectively, and Ted Cruz defeated David Dewhurst. Grayson ended up going to Harvard and heading a Democratic super PAC; Crist and Specter left the GOP entirely.

Paul, Rubio, Toomey, and Cruz were all November success stories as well. Christine O’Donnell, Sharron Angle, Ken Buck, and Richard Mourdock all won their primaries but lost the general election, keeping Republicans from picking up the seats they need to win the Senate majority.

In evaluating why Tea Party candidates are struggling, this is as good a place as any to start. Many Republicans, even those who are very conservative, do not trust Tea Partiers to close the sale in tough races. Consequently, they would rather go back to supporting imperfect Republicans to ceding Senate seats to Democrats.

O’Donnell’s problems were obvious from the start. But Buck and Mourdock were decent, if overly combative candidates. They and Angle began their races running well against their Democratic opponents, only to blow them in the homestretch. Even O’Donnell held one slim lead in a Rasmussen poll, clearly an outlier.

Plenty of establishment candidates have also blown winnable Senate races in recent years, notably including Wisconsin’s Tommy Thompson in 2012. But complaining about double standards isn’t going to get more conservatives nominated and elected.

It’s also clear that the establishment is fighting back, trying to deny conservative groups primary victories so as to dry up their future fundraising and going so far as to support primary challenges to certain conservative incumbents.

They don’t have much to show for the latter project yet, as evidenced by Walter Jones winning his primary. But some key Tea Party groups—already in many cases under fire for not spending enough money on the races off which they fundraise—don’t have a good batting average this year.

Like past iterations of the conservative movement, the Tea Party has helped pull the Republican establishment to the right. After Ronald Reagan, Republican presidential candidates stopped sounding like Gerald Ford or Richard Nixon. Mitt Romney and George W. Bush use more conservative rhetoric than George Romney or George H.W. Bush.

Jon Huntsman, widely considered a “liberal” Republican in the 2012 presidential primary, had a record and platform to the right of 2008 nominee John McCain’s.

It takes more than red meat to chop the federal government back down to its constitutional size, however. And in a political climate where Republican bosses are starting to hit back and rank-and-file primary voters are recovering their desire to win at all costs, bad Tea Party candidates have the potential to drag the good ones down with them.

Conservatives are used to this dilemma. Indiscriminately voting for every politician with an “R” next to his or her name doesn’t produce conservative government even if the Republican wins in November. And neither does sending up conservative-sounding candidates who lose.

W. James Antle III is editor of the Daily Caller News Foundation and author of Devouring Freedom: Can Big Government Ever Be Stopped?

Follow @jimantle