Some Trump allies even praised her, in an attempt to raise expectations ahead of the fall campaign. Senator Lindsey Graham, the South Carolina Republican who is one of the president’s closest allies on Capitol Hill, called Ms. Harris “smart” and “aggressive” and predicted she would be a “formidable opponent.”
But some Republicans, including ones often critical of the president, cautioned that presidential tweets and pundit chatter would not have nearly the impact on voters that advertising would. And the Trump campaign’s ability to be more focused and consistent in its messaging online and on television is where it can do the most potential damage by defining an opposing running mate.
“They can’t control Trump,” said Mike Murphy, a media adviser to several Republican presidential candidates. “He’ll be tweeting, name calling — and the difference between this time and last time is that Trump has half a billion dollars in resources at his disposal from the R.N.C.”
Mr. Murphy said that Ms. Harris, and her support for certain policies, would be easier for conservatives to attack than their initial, disjointed, response suggests. “The machinery under the Trump campaign knows how to do the mediocre, standard version of this,” he said. “Kamala Harris is the pick. Here’s the résumé: As attorney general she opposed the death penalty, even for cop killers; as senator, she supported reparations for slavery and said she would take away private health insurance. She is the future.”
On Wednesday, Mr. Biden made it clear he expected the campaign to go in the opposite direction, and become more personal.
“Donald Trump has already started his attacks, calling Kamala ‘nasty,’ whining about how she’s ‘mean’ to his appointees,” he said. “Is anyone surprised Donald Trump has a problem with strong women across the board? We know that more is to come.”
But Mr. Trump has struggled to define Ms. Harris with that kind of precision since the Democratic primary, when he failed to land on a quick-hit way to undermine her candidacy. The president reveled in battering Senator Elizabeth Warren of Massachusetts as “Pocahontas” and making fun of Mr. Biden’s mental acuity by referring to him as “Sleepy Joe.”