With Dueling Ads, Harris and Trump Both Try to Define Her as a Candidate

The race to define Vice President Kamala Harris began in earnest on Tuesday, with both her campaign and former President Donald J. Trump’s team unveiling television advertisements that aim to explain her biography to voters in battleground states.

Ms. Harris’s new ad, her first since becoming the party’s de facto nominee, labels her as “fearless” while leaning into her time as a local and state prosecutor. “She put murderers and abusers behind bars,” a narrator states. “Kamala Harris has always known who she represents.”

Mr. Trump’s new ad, meanwhile, attacks her as being weak on the border. It suggests that she is responsible for millions of border crossings and a quarter-million deaths from fentanyl, which the ad says occurred “on Harris’s watch.” It closes with a new Trump tagline for Ms. Harris: “Failed. Weak. Dangerously Liberal.”

Just over a week ago, Ms. Harris replaced President Biden as the Democratic Party’s standard-bearer. Despite being the vice president and having represented the nation’s largest state as one of California’s senators, Ms. Harris is relatively unknown by many of the voters in battleground states who are likely to decide the presidential election.

The new ads will cost tens of millions of dollars and run in those key states.

Ms. Harris’s spot is the beginning of what her campaign has said is a $50 million blitz before the Democratic National Convention, which begins on Aug. 19 in Chicago. (The campaign has announced roughly the same amount of ad spending in the previous several months.)

The Trump campaign is spending more than $12 million across Arizona, Georgia, Michigan, Nevada, Pennsylvania and Wisconsin over the next two weeks, according to data from AdImpact, a media-tracking service — its first major television ad purchase since Mr. Biden made way for his vice president.

The Harris campaign said its ads would run in 60-second increments on broadcast television during the Olympics, among other programming, and appear in shorter versions online.

“Kamala Harris has always stood up to bullies, criminals and special interests on behalf of the American people — and she’s beaten them,” said Jen O’Malley Dillon, Ms. Harris’s campaign chair. “This $50 million paid media campaign, bolstered by our record-setting fund-raising haul and a groundswell of grass-roots enthusiasm, is one crucial way we will reach and make our case to the voters who will decide this election.”

Ms. Harris’s ad also leans into an argument that she represents the future while Mr. Trump, 78, stands for the past — a case that is far easier for Democrats to press with the vice president, who is 59, at the top of the ticket rather than the 81-year-old Mr. Biden.

“Donald Trump wants to take our country backward,” Ms. Harris says in the ad. “To give tax breaks to billionaires and big corporations and end the Affordable Care Act. But we are not going back.”

Mr. Trump’s ad aims at what his campaign believes is one of Ms. Harris’s biggest weaknesses: the Biden administration’s border record.

In speeches over the past week, Mr. Trump repeatedly criticized Ms. Harris’s work as the “border czar,” a position she was never officially given but that refers to her being deputized by Mr. Biden to try to address the root issues causing people to flee countries in Central America. Ms. Harris was not responsible for overseeing border security.