In a tight runoff contest, Sen. Thad Cochran manages to eke out a victory against his tea party challenger, Chris McDaniel.​ (WLOX)

There was Sen. Thad Cochran (R-Miss.). And there was everybody else.

Among the Republican senators facing tea party primary challengers this year, Cochran long appeared the most likely to lose. His opponent was a national tea party star. Cochran made no efforts to warm up to the forces trying to dislodge him. He hadn't run in a campaign so competitive in decades.

But he survived a nasty, expensive battle Tuesday, dealing a huge blow not only to challenger Chris McDaniel, but to everyone in the tea party movement hoping to unseat a Republican senator in a primary for the third straight election cycle.

Last December, more than half the Senate Republicans running for reelection had primary challengers who were threats or potential threats. So far, none have panned out. The window has now shrunk to two races: Kansas and Tennessee.

The incumbent looks pretty safe in both states. Sen. Lamar Alexander (R-Tenn.) prepared very early in the election cycle, rounding up support from influential Republicans. Challenger Joe Carr (R) has not won backing from national groups as McDaniel did. The primary is Aug. 7.

In Kansas, Sen. Pat Roberts (R) made news for all the wrong reasons in February when he revealed that he stays with supporters when he returns to the state and leases out the home he owns there. (Being perceived as out of touch like that can be disastrous. Just ask Dick Lugar.)

But the momentum of physician Milton Wolf was blunted just weeks later by a story about him cracking jokes about graphic X-ray images online. He has struggled keep up with Roberts in the money chase leading up to the Aug. 5 primary.

The top-two ranking senators -- Minority Leader Mitch McConnell (R-Ky.) and Minority Whip John Cornyn (R-Tex.) -- once looked vulnerable to the political right. But each one easily got past challengers who never gained traction. Sen. Lindsey Graham (R-S.C.), a moderate on the hot button debate over immigration who has irked many activists, also skated to victory.

Until recently, it was extremely rare for a senator to lose in a primary. So rare that it only happened four times between 1982 and 2008.

But then came the rise of the tea party in 2010.  That year, it took down Robert Bennett in Utah. The movement's big primary triumph over a siting senator in 2012 came when it toppled Lugar in Indiana.

Cochran represented the best chance to make it three in a row. But his win makes it increasingly likely that 2014 will go down as the year Senate Republicans found their footing against tea party insurgents.