Harris’s Ad-War Message: Trump Is Pro-Billionaire, She Worked at McDonald’s

Flush with cash and fresh off the Democratic National Convention, Vice President Kamala Harris’s campaign is flooding the airwaves and the internet with advertising that is meant to combat an overarching weakness: Voters trust former President Donald J. Trump more than her on the economy.

The ads, targeted to the battleground states, lean into Ms. Harris’s middle-class background. They aim to tell Americans that she is the candidate who understands the pain of stubbornly high prices and can help tame inflation, pointing to her plans to lower the cost of housing, food and other daily necessities while calling Mr. Trump an ally of billionaires and giant corporations. They are being complemented by similar spots from the biggest super PAC supporting her, Future Forward.

The Harris campaign said it spent $150 million on ads in August and announced that it would reserve $370 million worth of ads between Labor Day and the November election. Digital ads will account for $200 million of that spending in the coming months, a tremendous sum that underscores the increasing need to reach voters on their phones and other devices.

For Ms. Harris, the new wave of ads signals a shift in message and tone from President Biden on the economy.

Mr. Biden, who has worked in and around politics since 1970, sometimes struggled to express empathy for the high costs frustrating Americans, preferring to talk about other indicators that showed the economy was doing well. Ms. Harris, for her part, is trying to run as a change candidate — despite her status as a vice-presidential incumbent — so she can free herself from the burden of Mr. Biden’s record and draw a contrast with Mr. Trump.

Ms. Harris has rolled out roughly half a dozen new ads over the last