The first sign that Republican leaders could not control their new majority came on a vote to help Americans who lose their jobs to foreign workers. House Majority Leader Eric Cantor (R-Va.) considered the measure routine and in February 2011 put it on a list of bills expected to pass without objection.

Enter the Club for Growth. Flush with power after helping to elect 13 House members and defeat two veterans in the Senate, the conservative campaign-finance machine blasted out an e-mail declaring its opposition to extending the 40-year-old retraining program, which it called “inappropriate for a country devoted to free markets and a limited government.”

Within hours, like-minded lawmakers protested. Cantor abruptly canceled the vote in a display of party chaos that was astonishing at the time.

It’s not so astonishing anymore. Since then, the Club for Growth has repeatedly embarrassed House leaders, helping to torpedo Speaker John A. Boehner’s “fiscal cliff” strategy, the recent farm bill — even bland Cantor initiatives aimed at helping the uninsured and sick kids with cancer. After spending millions to empower the anti-government right, the Club has become the proud sponsor of congressional gridlock.

Now the group is advocating disruption on a grander scale, urging Republicans to wage what some in the party are calling a suicidal campaign to shut down the government unless President Obama agrees to defund his signature health initiative. Last week, Boehner (R-Ohio) canceled another vote — this time on a plan to keep the government open past Sept. 30 — after the Club and other outside groups complained that it failed to undermine Obamacare.

The conservative political action committee Club for Growth injected more than $55 million into the past four election cycles, spending more money each year with a varied, but improving, success rate. Since 2006, Club for Growth has helped nearly 50 endorsed candidates get elected to Congress, driving Republicans in the House — and increasingly in the Senate — further to the right. The group rarely follows through on threats to challenge incumbent Republicans, but when it does, it has been throwing increasingly larger sums of cash at its targets.

“Every Republican ran on defunding or repealing Obamacare. This is a test of whether they’re actually going to do what they say they’re for,” said Club President Chris Chocola, a former congressman from Indiana. “What’s the more radical thing to do: Continue to spend more and borrow more from China? Or have the confrontation? It’s never going to get any easier.”

GOP leaders are reworking the measure while Washington braces for another round of white-knuckle deadlines. Meanwhile, Republican strategists are fuming, accusing the Club and its allies of dividing the party and toying with the U.S. economy in a cynical bid to raise cash.

“These are self-perpetuating entities, and if they stop fighting for a cause, the money dries up. So they have to drum up this outrage because it pays their salaries,” said former Arizona congressman Ben Quayle, the son of former vice president Dan Quayle. Ben Quayle narrowly lost his House seat last year after tangling with the Club. “It’s all about how to increase their fundraising,” he said.

Chocola is unapologetic. The Club’s mission, he said, is to advance “economic freedom, not Republicans.”

“It’s not our role to negotiate. It’s not our role to compromise. That’s not what we do,” he said in an interview at the Club’s offices on L Street NW. “We try to find the most pro-growth position and push people as close to that as we can.”

Founded in the early 1980s by a small band of New York money managers, the Club for Growth has long been the premier financier for conservatives who hate taxes, love free trade and oppose just about every category of federal spending. The Club has done more than any group to purge moderates from the GOP; now it is seeking to enforce the rigid ideological standards that win votes on the campaign trail but make it hard to govern.

These days, the Club is not alone. FreedomWorks, Americans for Prosperity, even the venerable Heritage Foundation are all trying to harness the energy of the tea party movement. What makes the Club the heavyweight is money — and its relentless focus on Republican primaries.

In the 2012 election cycle, the Club and its various entities spent more than $9 million trying to ensure favored candidates won GOP primaries, more than twice as much as they spent trying to defeat Democrats, according to Traditionally, they have also been the only group willing to target incumbents they deem RINOs, “Republicans in Name Only.”

Over the years, the Club has elected 15 to 20 die-hard loyalists in the House. On some issues, it can sway 45 votes or more, according to a Washington Post analysis. Boehner can afford to lose only 16 Republicans to pass a bill without Democratic votes.

As a result, the Club often swings a bigger stick even than Grover Norquist, the anti-tax activist. In December, Norquist endorsed Boehner’s “Plan B” strategy to avoid a broad New Year’s Day tax hike by offering Democrats a compromise that would have raised taxes on income only over $1 million a year. The Club came out against the proposal. Hours later, in perhaps the biggest humiliation of Boehner’s tenure, it was dead.

The same thing happened this past week. Norquist tacitly endorsed Boehner’s plan to keep the government open in exchange for a vote in the Senate that would require vulnerable Democrats to take a stand on Obamacare. The Club complained that the “smoke and mirrors” measure would not block implementation of the law and urged Republicans to vote no.

In an interview, Norquist dismissed the Club and its allies as dilettantes uninterested in the success of their legislative strategies. He said rejecting Plan B was a tactical blunder that weakened GOP negotiators and probably cost the nation $100 billion in higher taxes. And defunding the Affordable Care Act has no hope of winning Obama’s signature, he said.

“If you’re trying to maintain a movement, you’ve got to have legislative victories,” Norquist said. “There’s no point in building a powerful movement on the back of legislative failures.” He is urging Republicans to try to persuade Obama to delay key provisions of the health law, including the individual mandate.

Norquist noted that the Club and its allies also opposed the 2011 debt-limit deal, which led to more than $2 trillion in spending cuts over the next decade, including the sharp cuts known as the sequester. Instead, they demanded a constitutional amendment to balance the budget.

“A tremendous victory was won by having a flexible approach to progress,” Norquist said. In a negotiation, “it isn’t one thing you want — there are 20 things you want. . . . You can’t get caught up in ‘my tactic, right or wrong.’ ”

Senior Republicans play down the Club’s significance.

“They may be claiming more influence than they’ve actually got,” said Rep. John Kline (R-Minn.), one of Chocola’s best friends from his days on the Hill.

Still, that influence seems to be spreading. In the once-collegial Senate, bomb-throwers such as Republicans Ted Cruz (Tex.), Mike Lee (Utah) and senator-turned-Heritage-Foundation-president Jim DeMint (S.C.) were Club candidates. The Club also championed Marco Rubio (Fla.), Rand Paul (Ky.) and Patrick J. Toomey (Pa.).

“The Club for Growth is probably America’s most influential advocacy group in the space of economic and fiscal policy,” said Toomey, who served as the Club’s president from 2005 to 2009. “There’s a national movement that has been increasingly frustrated with Republicans who are not consistent advocates for limited government and economic freedom. And that’s been a source of the Club’s strength.”

Critics love to point out that Chocola, 51, was hardly a purist in Congress. He voted to raise the debt limit and create the Medicare prescription drug program, which — unlike Obamacare — went directly onto the federal credit card. (“I wake up in a cold sweat every other day because I did that,” he said ruefully of the Medicare vote.)

He lost his seat to a Democrat in 2006 after inviting President George W. Bush to a town hall meeting where 8,000 people showed up to hear Bush’s plan for introducing private accounts to Social Security.

After taking that risk with his political career, Chocola said: “I get back to Washington, and the Republican leadership says we can’t do that because it’s too hard. So, to me, that was like, ‘Well, why do we care about the majority if we’re not going to use it do things that we say we’re for?’ ”

Chocola came to the Club in 2009, just as the tea party was emerging. Under his leadership, the Club’s hand has been hot. In 2010, the Club not only chased veteran Arlen Specter (Pa.) out of the Republican Party — he eventually lost the Democratic primary and Toomey won his seat — but also took out Sen. Robert F. Bennett (R-Utah), who made the mistake of championing universal health insurance. Last year, the Club spent roughly $5 million to promote the long-shot Cruz over Texas Lt. Gov. David Dewhurst.

And the Club vows to be more aggressive in 2014. It has set up a Web site, Primary My Congressman, aimed at crowdsourcing challengers to House moderates. So far, it has found one, to run against Rep. Mike Simpson (R-Idaho), a close Boehner ally.

The normally loquacious Simpson did not respond to requests for comment. But former congressman Steven C. LaTourette (R-Ohio), leader of the centrist group Main Street Advocacy, quickly vowed to defend him, calling the Club for Growth “a cancer on the Republican Party that prides itself on supporting rigid, divisive and obstructionist candidates.”

Simpson marks the Club’s 10th targeted incumbent since 2006. Three were replaced by Club candidates, and three seats were lost to Democrats after Club candidates proved unpopular with general-election voters. (The Club later reclaimed one seat, electing Maryland state Sen. Andy Harris in the Eastern Shore district once held by moderate Wayne T. Gilchrest).

Three others survived. GOP strategist Brock McCleary, who worked on the House Republican campaign committee in 2012, said he tried to calm incumbents by pointing out that they are “more likely to get run over by a car than lose a primary.” But the Club’s power, McCleary said, is “not always based on fear of loss. It’s the fear of the money and effort it would take to fend off a challenger.”

The Club is financed by a small group of big donors, many of them company founders and entrepreneurs. Seven people gave the Club at least $1 million for the 2012 elections, according to the Center for Public Integrity, including Club Chairman Jackson T. Stephens Jr. of Arkansas, whose family underwrote the initial public offering for Wal-Mart in 1970.

Three others rank among the nation’s top 25 political donors, according to the center: Perry Homes founder Bob Perry of Texas, who died in April; private equity giant John Childs of Florida; and PayPal co-founder Peter Thiel, who helped bankroll the presidential campaign of then-Rep. Ron Paul (R-Tex.).

The group also gathers contributions from thousands of members and delivers them directly to candidates it has endorsed. All told, the Club says it spent about $17 million to support its picks last year and bundled another $7 million for their campaigns.

Chocola said he is not trying “to make people miserable” but to push the party to live up to its own economic claims, to make the case for smaller government in a “clear and convincing way.”

“The world has changed,” he said. “All we’re trying to do is get the Republicans to think about what they’re doing rather than continually do these things that were done out of habit, from a transportation bill to a farm bill. We may not win every battle, but we at least get to have the debate: How much are you spending? Is it good policy? Who’s going to pay for it?

Chocola said he has “great respect” for House Minority Leader Nancy Pelosi (D-Calif.) because, as speaker, “she knew she could lose her majority doing something she believed in called Obamacare. And public opinion was against her. And she lost the House. But today, it’s the law.”

Republican leaders, by contrast, have had to be dragged, kicking and screaming, to implement the sequester and to offer a budget that balances in 10 years, Chocola said. Still, those things have happened. “So we like the direction,” he said. “But our job is never to be satisfied.”

Paul Kane contributed to this report.