Washington • A conservative group will air an ad in Utah for 10 days starting Thursday that says Sen. Mitt Romney has been “exposed by news reports as a Democrat secret asset” because of his previous support and now criticism of President Donald Trump.

The Club for Growth ad, airing on Fox News statewide, starts with a narrator saying, “Slick, slippery, stealthy: Mitt Romney had us fooled.”

It then shows Romney praising Trump, first when Trump endorsed Romney in his 2012 presidential bid and years later when Romney was a potential pick to be Trump's secretary of state. The Club for Growth is spending $25,000 for the 10-day cable buy.

The ad comes after Romney said it was “troubling in the extreme” that Trump had asked a foreign power – the president of Ukraine – to investigate a political rival, former vice president and Democratic presidential nominee Joe Biden. Romney later said it was “wrong and appalling” when Trump also suggested China look into Biden and his son Hunter Biden and their dealings in that country.

The Utah Republican has been one of few Republicans willing to break ranks and criticize the president over his attempts to have Ukraine investigate Democrat Joe Biden and his son. The president responded by calling Romney a “pompous ass” and labeling him a “pompous senator.”

Club For Growth's ad says that Romney's “cover's blown.”

“Sources say Romney’s plotting to take down President Trump with impeachment,” the ad says, without citing any sources. “Tell Romney, quit colluding with Democrats on impeachment.”

Romney has not backed the impeachment inquiry launched by House Democrats, but has not opposed it, either.

The senator’s office declined comment on the ad.

Club for Growth has been a longtime supporter of Sen. Mike Lee, R-Utah, who is opposing the impeachment probe and has defended Trump.

David McIntosh, the president of Club for Growth, said the ad was aimed at getting conservatives in Utah to call on Romney to “stop working with Democrats to impeach President Trump.”

“There are two things Sen. Romney is good at: changing positions and alienating conservatives, and now he is bringing his unique brand of self-promoting flip-flopping to yet another issue,” McIntosh charged.

As far as changing positions, it appears that Club for Growth has done exactly that in its view of the president.

During the 2016 campaign, the group spent $2 million on anti-Trump ads, spurring then-candidate Trump to tweet “The Club for Growth is a very dishonest group. They represent conservative values terribly & are bad for America.”