WASHINGTON — In a suburban Chicago district, Kelly Mazeski, a breast cancer survivor, used the day of the vote to repeal the Affordable Care Act to announce her House candidacy, vowing to make Representative Peter Roskam pay for his vote “to make Americans pay more and get less for their health care.”

In western New York, Lt. Gov. Kathy Hochul has stirred talk of a congressional race with her slashing criticism of Representative Chris Collins, who rallied fellow Republicans to vote for the health measure, then conceded in a national television interview that he had not read the bill.

And in suburban Philadelphia, Chrissy Houlahan, an Air Force veteran challenging Representative Ryan A. Costello, said she would make Mr. Costello’s decision to support the bill in committee, before opposing it on the floor, a central issue.

It is far too early to determine whether 2018 will bring a political wave, but the House’s approval of a deeply unpopular health care bill on Thursday has handed Democrats a potent line of attack for the midterm elections. While Republicans believe that fulfilling a seven-year promise on health care will energize their base next year, Democrats are anticipating a backlash that may put in jeopardy a Republican House majority that once seemed unshakable.