Is the tea party over?

Is tea party out of gas?

Is the tea party over?

It's certainly starting to feel that way in the 2014 GOP primary season as incumbents and establishment-backed candidates continue to rack up impressive wins over conservative insurgents.

Tuesday night was no different as Kentucky Senator Mitch McConnell crushed tea party-backed challenger Matt Bevin in a race once thought to present a serious challenge to the powerful minority leader.

Bevin enjoyed financial backing from the Senate Conservatives Fund and FreedomWorks but doomed himself with a clumsy campaign that included his appearance at a cockfighting rally and attacks on Wall Street bailouts he previously supported. McConnell wound up with over 60 percent of the vote, barely breaking a sweat.

Senate Minority Leader Mitch McConnell, R-Ky.
Bill Clark | CQ Roll Call | Getty Images

In several other states Tuesday night, incumbents also fared well, with Idaho Rep. Mike Simpson and Pennsylvania Rep. Bill Shuster taking down tea party challengers. The Chamber of Commerce rode to the rescue of a number of incumbents with tough races on Tuesday, running a series of supportive ads. The chamber's preferred candidates won in every case.

Read More Why these elections matter for the US Chamber of Commerce

And in Georgia, the GOP establishment got what it wanted by the defeat of a tea party challenger in the race to fill the seat of retiring Republican incumbent Sen. Saxby Chambliss. (Two mainstream Republicans, Rep. Jack Kingston and businessman David Perdue, face a runoff for the nomination.)

Georgia and Kentucky once presented Democrats with rare opportunities to pick off Republican seats in a year that clearly favors the GOP. Both seats now appear safer for Republicans.

Republicans also got a mainstream candidate in Oregon to take on Democratic incumbent Sen. Jeff Merkley. The GOP's candidate there, pediatric neurosurgeon Monica Wehby, has endured some negative press lately over her personal relationships, but she comes very much from the center of the GOP and not the conservative wing that dominated in 2010 and 2012.

All of Tuesday's wins for the establishment follow previous primary days that saw business-backed candidate Thom Tillis avoid a runoff to take on vulnerable Democratic incumbent Sen. Kay Hagan in North Carolina and House Speaker John Boehner easily crush a challenge in Ohio. Many other incumbents have also dismissed challengers.

And the primary season itself comes on the heels of Boehner essentially breaking the back of the tea party movement in the House by getting a budget through that avoids any new government shutdown or debt ceiling fights this year.

The GOP is now poised to add to its House majority and give itself a solid chance of picking up the six seats needed to take the Senate.

Why is all this happening?

Partly it's because the GOP learned from bitter experience in 2010 and 2012 that untested conservative insurgent candidates such as Todd Akin can cost the party its shot at a Senate majority. Things will get much harder for Republicans in 2016, both given the number of vulnerable incumbents and the nature of electorate. If they are going to get the Senate, it has to be in 2014. Even then, holding it in 2016 will be a huge challenge.

Read More Political brand names could give some Dems an upside

The party also spent the early part of this year drilling into incumbents that they can't expect to just coast through primaries, especially not with the flood of unrestricted Super PAC money that can quickly swamp an unprepared sitting member of Congress.

But a good deal of the current political trend is the result of a very different fiscal and economic background from 2010 and 2012.

The soaring deficits that drove the rise of the tea party in 2010 are now half the size they were and getting smaller (at least for the next few years). The economy is expected to grow at a 3 percent or faster clip the rest of this year and the unemployment rate is trending down, especially the short-term rate, which is back to where it was before the financial crisis.

This is hardly to say that there is not still widespread frustration with the pace of economic growth and the nature of jobs being created or the long-term trajectory for federal debt.

Much of the debate over what to do about this will continue to play out and tea party candidates able to harness a Republican version of anti-Wall Street, anti-crony capitalist sentiment will be potent in both 2014 and 2016.

Read More Dems, GOP using hot button issues to turn out the vote

But movements like the tea party always tend to rise during periods of economic crisis and fiscal profligacy only to subside when things improve. So the decline should be no great surprise.

And tea partyers can take great solace in the fact that their efforts led to budget deals that did in fact slash near-term deficits (much to the chagrin of "anti-austerians") and stiffened backbones of incumbent Republicans who had grown too comfortable in their jobs. In large measure, the tea party lost by winning.

CORRECTION: This story was revised to show it was Pennsylvania Rep. Bill Shuster who defeated a tea party challenger.

—By Ben White. White is Politico's chief economic correspondent and a CNBC contributor. He also authors the daily tip sheet Politico Morning Money [politico.com/morningmoney]. Follow him on Twitter @morningmoneyben.