(CNN) - Is Mitt Romney running again?
"The stakes are very high in this election because Washington's spending is out of control," says Mitt Romney in a new campaign commercial, sounding very much like a candidate running for office.
But in the ad, the former Massachusetts governor and 2012 Republican presidential nominee goes on to say, "You can take it from me, the conservative choice for Congress is Mike Simpson."
"I know because I've seen him in action. Mike is fighting hard every day to cut Washington's wasteful spending, to stop junk lawsuits and to fight against Obamacare."
Romney, who has ruled out another bid for the White House, stars in the new spot for Simpson, which was put out by the U.S. Chamber of Commerce.
The eight-term congressman faces a tough challenge from the right in Idaho's May 20th primary from Bryan Smith, an attorney who claims that Simpson is not conservative enough and is soft on spending. Smith is backed by some tea party groups and by the DC-based anti-tax group Club for Growth, which has a history of backing conservative primary challengers. The group has gone up with some spots critical of Simpson.
Romney endorsed Simpson last November.
"We are going to win this battle. I hope you'll join me and strongly support Mike Simpson for Congress," Romney says at the end of the spot.
Romney's starring role in the commercial is the first time he's appeared in a campaign ad this cycle.
Simpson represents Idaho's 2nd Congressional District, which stretches from Boise to the borders with Wyoming and Montana and covers the entire eastern and most of the central parts of the state. Romney's backing could especially help in eastern Idaho, which has a large Mormon population.
Simpson was an early supporter of Romney's 2012 presidential bid.
Simpson is also being backed by House Speaker John Boehner and other members of the House GOP leadership.
"The U.S. Chamber is proud to stand with Governor Mitt Romney in support of Mike Simpson, the conservative choice for Congress in Idaho's second district. Mike Simpson has a proven record fighting for Idaho values and policies that support job creation and economic freedom. He has received a 92% lifetime rating with the U.S. Chamber," said Rob Engstrom, the Chamber's national political director.
The Chamber tells CNN that their commercial will start running Wednesday on broadcast and cable in the Boise, Idaho Falls-Pocatello, and Twin Falls TV markets.
Romney may have enjoyed some political payback, courtesy of his son Josh.
Two years after Senate Majority Leader Harry Reid, during the 2012 presidential election, repeated an unsubstantiated report that Mitt Romney had not paid his taxes, Josh Romney tweeted Tuesday tweeted a photo of his father standing in line to pay his taxes.
Tuesday was the deadline for income earners to file their tax returns.