“Republicans have followed Donald Trump off the side of a cliff,” David Urban, a longtime Trump adviser with ties to Pennsylvania, said in an interview.

Former Representative Peter King, a Republican from Long Island who has long supported Mr. Trump, said, “I strongly believe he should no longer be the face of the Republican Party.” He added, “His self-promotion and his attacks on Republicans including Ron DeSantis and Mitch McConnell were largely responsible for Republicans not having a red wave. We can’t allow blind fealty to Trump to determine the fate of our party.”

“Almost every one of these Trump-endorsed candidates that you see in competitive states has lost,” Chris Christie, the former New Jersey governor, said Wednesday on ABC’s “Good Morning America.” “It’s a huge loss for Trump. And, again, it shows that his political instincts are not about the party, they’re not about the country — they’re about him.”