WASHINGTON—Four House Republicans embroiled in scandals are further complicating their party’s struggle to maintain a House majority in the midterm elections.

On Thursday, the nonpartisan Cook Political Report changed its forecasts for the districts of two GOP representatives, Rod Blum of Iowa and Scott Taylor of Virginia, into more competitive territory for Democrats, citing recent “bad headlines.” The move comes days after two other previously solid Republican districts were assessed to have tightened as GOP candidates’ faced legal troubles.

With elections just weeks away, the individual scandals could spell broader trouble for the GOP, poll watchers say.

“An incumbent can survive a great deal in an election year that’s favorable to his or her party,” said Larry Sabato, director of the University of Virginia Center for Politics. “But if there is a wave crashing for the other party, a scandal is extra weight that can cause a candidate to sink.”

Democrats need to achieve a net gain of 23 seats to seize control of the 435-seat chamber. When the president’s approval rating is below 50%, as President Trump’s is, the party in control of the White House has lost an average of 40 House seats in midterm elections. A large number of retirements from House Republicans have added to a competitive environment where Republicans can’t afford to have more districts in jeopardy.