The Club for Growth, a perpetual thorn in the side of many Republican operatives, took a hit Tuesday in Mississippi, where Sen. Thad Cochran survived a primary challenge despite a significant investment from the anti-tax group.  

The Club for Growth’s super PAC arm spent $2.4 million against Cochran, according to figures compiled by the Center for Responsive Politics. That’s a significant chunk of the $3.8 million it’s expended so far this cycle against Republicans.  

What’s more, the defeat of state Sen. Chris McDaniel means the club has now failed to topple arguably its top two GOP incumbent targets of the midterm cycle — Cochran and Rep. Mike Simpson. The club spent nearly $500,000 for Bryan Smith, who lost his May 20 challenge to the Idaho Republican.  

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In a Wednesday morning statement, Club for Growth President Chris Chocola delivered an optimistic message about the group’s potential to still help add to the “ranks of pro-growth Senators,” highlighting its endorsements in Alaska, Arkansas and Nebraska races.  

“We are proud of the effort we made in Mississippi’s Senate race and we congratulate the winner,” said Chocola, a former Indiana congressman. “We expect that Senator Cochran and others gained a new appreciation of voter frustration about the threats to economic freedom and national solvency.”  

The three Republican Senate candidates it is now backing are Ben Sasse, who is heavily favored to win Nebraska’s open seat; Rep. Tom Cotton, who is taking on Democratic Sen. Mark Pryor in Arkansas; and Dan Sullivan, one of three Republicans vying to take on Alaska Democratic Sen. Mark Begich.  

The club’s PAC is currently supporting five House candidates in New Hampshire, Alabama, Georgia and Texas, plus two incumbents: Reps. Mike Pompeo of Kansas and Justin Amash of Michigan.  

At the start of the 2014 cycle, the club offered up 10 House Republicans as bait for conservative activists and donors via its PrimaryMyCongressman.com website. More than a year later, only one of those members — Simpson — had a significant primary challenge.  

The club’s stated goal is to increase the number of members of Congress who support its “pro-growth, free-market policies” and ultimately to affect the legislation that emerges from Capitol Hill. Among the current Republican senators it previously endorsed are Tom Coburn of Oklahoma, Marco Rubio of Florida and Ted Cruz of Texas.  

Both Simpson and Cochran rank toward the bottom of the GOP on the club’s legislative scorecard — which members are reminded about before every vote that will be included in their score — but the two Republicans are headed back to Capitol Hill next year for another term.  

What rankles Republicans working to expand the number of congressional seats the party controls, regardless of ideological purity, is the amount of money the club spends against GOP candidates — money other Republicans wish the group would instead use to oust Democrats.  

In 2012, the club’s super PAC spent more than $9 million against Republicans, though $5 million of that was against Texas Lt. Gov. David Dewhurst — on behalf of Cruz — in the prohibitively expensive Texas media markets. It also dropped nearly $1 million in an Indiana race against then-Sen. Richard G. Lugar, who lost his re-nomination bid to state Treasurer Richard Mourdock. Democrat Joe Donnelly defeated Mourdock in the general.  

The primary spending also forces other GOP groups — including the National Republican Senatorial Committee in Cochran’s case — to expend precious resources to defend incumbents against fellow Republicans, instead of on the goal of winning the Senate majority or expanding the party’s majority in the House.  

Main Street Advocacy President Steven C. LaTourette, whose group spent money to defend both Cochran and Simpson, poured salt in the club’s wound in a Tuesday night statement, calling Mississippi the club’s “last chance to salvage an otherwise dreadful primary season for them.”  

“This year’s elections have exposed just how disconnected the Club for Growth is from actual Republican primary voters,” LaTourette said. “The most high profile primary win over an incumbent came in the defeat of Eric Cantor — the one race the Club wasn’t involved in.”  

The Club for Growth hasn’t been successful in every race this cycle, and its spending against fellow Republicans is viewed by many party operatives as unhelpful to the cause of controlling Congress. Still, Phillip Stutts, a veteran Republican consultant who worked for unsuccessful club-backed House candidate Chad Mathis of Alabama, said the group’s efforts are ultimately beneficial for the party.  

“Candidates and incumbents can’t take anything for granted anymore,” he said. “They have to watch their votes, they have to listen to their constituents and they have to pay attention.”  

Emily Cahn contributed to this report.