The conservative Club for Growth will launch a new round of TV and digital ads targeting four Republican lawmakers for supporting the Export-Import Bank, exposing the tension between the pro-business and tea-party wings of the party.

The ads will begin Friday in the home districts of Reps. David McKinley of West Virginia, Rob Bishop and Chris Stewart of Utah, and Bill Shuster of Pennsylvania, a spokesman for the group said Wednesday.

The spots, which will air on both broadcast and cable networks, are part of $1 million campaign from the Club timed to coincide with Congress's debate over reauthorizing the Ex-Im Bank. (The bank is better described as a government credit agency that backs loans to foreign entities as incentive to sign deals with U.S. companies. The Club sees this as corporate welfare.)

The first phase of the Club's campaign began last month, a spokesman said, while the third and final part will likely air next week. The spokesman said the group would spend $250,000 on TV targeting the congressmen, with an additional $30,000 reserved for digital ads targeting McKinley, Bishop, Stewart, and Shuster.

In the TV spots, the lawmakers are criticized for supporting a "petri dish of corruption and graft." In Bishop and Stewart's case, they are compared unfavorably to fellow Republican colleagues Sens. Mike Lee and Orrin Hatch. In West Virginia, the Club said McKinley supported a program backed by Hillary Clinton and Barack Obama.

"It spends billions of tax dollars on a handful of giant corporations," the spot running in McKinley's district says.

The ad running in Shuster's central Pennsylvania district likely will draw the most attention: In it, a narrator says there is a "scandal around Congressman Bill Shuster," referencing the revelation that the chairman of the Transportation and Infrastructure Committee has a romantic relationship with an airline lobbyist—one that has elicited cries of a possible conflict of interest.

The narrator continues to say, "No, not that scandal," before criticizing Shuster about the bank.

Shuster has said his office has a policy in place that prevents her from lobbying him on any issue.

Shuster, who has served in the House since 2001, already has drawn the threat of a serious primary challenge from Tom Smith, Pennsylvania's 2012 Senate GOP nominee. Shuster fended off a primary challenge last election cycle, winning by 18 points.

The battle over the Export-Import Bank has become a showdown between the GOP's conservative wing, led by groups such as the Club, and its business-friendly establishment allies, led by the Chamber of Commerce. The Chamber has waged an aggressive campaign of its own to push lawmakers into supporting the institution.

The first phase of the Club's campaign targeted Reps. Earl "Buddy" Carter of Georgia, Renee Ellmers of North Carolina, Stephen Fincher of Tennessee, and Bill Flores of Texas.

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