Just as his colleagues in the Senate majority were on the verge of ramming through President Trump’s second Supreme Court nominee, Mr. Flake, the independent-minded Republican from Arizona serving his last months in the Senate, threw up a roadblock. But in the end, he may have cleared the way for the confirmation and saved Republicans from themselves.

Provided the new investigation doesn’t turn up damaging information, the inquiry could ultimately make it easier for uncertain Republicans to back Judge Kavanaugh as soon as this week. It could also temper the perception that Republicans were much more interested in getting Judge Kavanaugh onto the court as quickly as they could rather than determining the validity of sexual misconduct accusations against him.

“It is reassuring to the public,” Senator Susan Collins, a Maine Republican and an ally of Mr. Flake, said in an interview. “It shows that Republicans want to make sure that we have all the facts to make an informed decision.”