The Democrats’ capstone re-election victory of Senator Raphael Warnock forced Republicans to reckon on Wednesday with the red wave that wasn’t, as they turned with trepidation to 2024 and the intensifying divisions in the party over former President Donald J. Trump.

Mr. Warnock’s two-and-a-half percentage point win over Herschel Walker in the Georgia Senate runoff left Democrats with a 51-49 seat majority in the upper chamber, a one-seat gain. That came despite dire predictions for a blood bath for President Biden’s party.

It quickly had Republican fingers pointing every which way: at Senator Mitch McConnell of Kentucky, the Republican leader accused by detractors of abandoning or belittling embattled Republican Senate candidates; at Senator Rick Scott of Florida, the chairman of the National Republican Senatorial Committee, who many feel badly mismanaged the Senate Republicans’ campaign arm; and at Mr. Walker himself, for hiding and lying about his past, only to see the details stream out steadily over the course of his campaign.

But for a handful of Republicans, newly emboldened by re-election or retirement to say so aloud, the biggest culprit was Mr. Trump. In increasingly biting terms, they slammed him for promoting flawed candidates, including Mr. Walker, dividing his party and turning many swing voters against the G.O.P. for the third election cycle in a row.