After Donald J. Trump became the presumptive Republican presidential nominee, he marveled that his primary fight had wrapped up before the one between Hillary Clinton and Senator Bernie Sanders of Vermont.

Mrs. Clinton’s allies share that sentiment, and then some. While Mr. Trump reaches out to critics such as the conservative website National Review and the Iowa evangelical figure Bob Vander Plaats, and as he meets for an hour with Henry A. Kissinger, the former secretary of state, the battle between Mrs. Clinton and Mr. Sanders has grown caustic.

Mr. Sanders’s campaign manager, Jeff Weaver, denounced Representative Debbie Wasserman Schultz of Florida, the Democratic National Committee chairwoman, on Wednesday morning, suggesting that she was a “divider” and accusing her of inappropriately playing favorites in the primary fight. Ms. Wasserman Schultz has strenuously denied she is taking sides.

The delegate math remains impossible for Mr. Sanders without large numbers of superdelegates changing their support, and Mrs. Clinton’s vote totals in the Kentucky primary on Tuesday night hindered a potential talking point. Yet for Mr. Sanders, who has been discussing the issues that are now central to his campaign for decades, and who is finally finding a large audience, has shown no interest in going anywhere before the convention.