Former Governor Tommy Thompson issued a statement Wednesday condemning the national Club for Growth for getting involved in the Republican primary for U.S. Senate by attacking state Sen. Leah Vukmir (R-Brookfield).

“The national Club for Growth is at it again,” said Thompson. “I won the 2012 GOP primary for U.S. Senate despite Club for Growth’s attacks. Worse yet, the national Club for Growth never offered any help to my campaign in the general election which gave Tammy Baldwin a huge cash advantage. I condemned the Club’s attacks in the GOP primary in 2012 and now in the 2018 primary. They are wasting precious resources that would be better used in the general election to elect a conservative to the U.S. Senate from Wisconsin.”

In 2012, the Club for Growth supported former Rep. Mark Neumann in the GOP Senate primary instead of Thompson and Eric Hovde. The divisive primary left the Thompson campaign exhausted of funds, leaving the former governor vulnerable to attacks from the Democrats. Tammy Baldwin defeated Thompson in the November election 51.5 percent to 45.9 percent.

This election cycle, Club for Growth is backing Vukmir’s rival for the GOP nomination Kevin Nicholson. The organization recently announced a $2 million ad buy attacking Vukmir ahead of the August 14 primary. Nicholson’s billionaire backer Richard Uihlein is a major funder of Club for Growth.

The Club for Growth responded to Thompson’s criticisms on Twitter:

The Club for Growth’s attacks on Vukmir have been particularly controversial. In December, the Club for Growth criticized Vukmir for voting for Governor Scott Walker’s first budget after Act 10 passed in 2011. The organization was severely criticized by many conservatives, including Grover Norquist of Americans for Tax Reform.

The latest round of advertising by the Club for Growth attacking Vukmir managed to steer clear of attacking Walker’s record in its latest ad. The ad is more personal in nature and attacks Vukmir for evading an open records request, sending a letter to a judge on behalf of former state Rep. Bill Kramer (R-Waukesha) who was convicted of fourth-degree sexual assault, and voting to increase per diems for expenses for state legislators.

Vukmir’s billionaire backer Diane Hendricks is funding Wisconsin Next PAC which has launched an ad against Nicholson’s record as a former president of the College Democrats and his appearance at the Democratic Party national convention. Nicholson has switched parties, claiming that his conversion to conservatism began while he was serving in Iraq.

The national Club for Growth is a different organization from the Wisconsin Club for Growth. Eric O’Keefe, the Director of Wisconsin Club for Growth, endorsed Vukmir in April.

Nicholson’s campaign also announced Wednesday that they are launching their first ad of the campaign, “Future.” The ad does not mention Vukmir. It focuses instead on Nicholson’s frustration with the lack of progress on immigration reform, repealing Obamacare and building a wall along the Mexican border.

The Thompson statement and the Nicholson ad comes at a time when momentum appears to have swung in Vukmir’s direction in the Republican primary. Vukmir now has a lead for the first time in the Marquette University Law School poll 34 percent to 32 percent, but well within the margin of error of +/- 7 percent. In June, Nicholson led 37 percent to 32 percent.