Rep. Tom PetriTom PetriDozens of former GOP lawmakers announce opposition to Trump Dem bill would make student loan payments contingent on income Black box to combat medical malpractice MORE (R-Wis.) could have a serious primary fight on his hands.

Wisconsin state Sen. Glenn Grothman (R), a conservative state legislator, announced Thursday that he'll challenge Petri for Congress.

"I will be filing a statement for candidacy later this week for the 6th Congressional District," Grothman said in a statement after saying Petri didn't have the "sense of urgency" he believes is needed to fight against government overreach.

Grothman, who's often an ally of Wisconsin Gov. Scott Walker (R), could give the 73-year-old centrist a tough race, assuming Petri runs for reelection.