A House panel approved the measure. But Republicans are divided over its size, cost and policy provisions, and many are concerned about the timing before the midterm elections.
Senator John Thune of South Dakota, the majority leader, openly questioned whether “the juice” was “worth the squeeze,” given the deep divisions in his conference over the measure.
The withdrawal came as polls show Americans opposing the president’s immigration tactics, and as some Republican lawmakers began to find ways to distance themselves.
The former lieutenant governor is the best-known candidate in a crowded field, but some state Democrats have cooled on him since he lost a Senate bid in 2022.
Mandela Barnes, the former lieutenant governor of Wisconsin, is a progressive who has maintained a large fund-raising network since his 2022 Senate race.