This election cycle is predicted to be the most expensive of all time, and one of the biggest expenditures for campaigns is political advertising.
David Broockman is a professor of political science at the University of California, Berkeley, and he has studied the effectiveness of political ads. He said political ad spending is increasing, in part, because recent elections have been so close.
According to FEC filings for January 2023 through September of this year, the Biden and Harris campaigns have spent nearly $320 million on "media buys and production." The Trump campaign's filings show nearly $77 million in spending on "placed media."
But research shows all that spending only influences a small number of voters. "We know from the research that most people are not persuaded by political ads. They have very small effects, but it's not exactly zero," said Broockman.
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Part of the challenge in trying to persuade voters is finding something to tell them they don't already know. Broockman used former President Donald Trump as an example. "What we saw in 2020, and are seeing again this year in 2024, with Trump on the ballot, voters really know a lot about Trump, and they kind of know how they feel about him. And so pro-Trump ads and anti-Trump ads just don't seem to be doing as much," he said.
But political ads aim to do more than just persuade voters. They're also used by campaigns to try to boost enthusiasm.
"But in this day and age, when there are so few [voters] on the fence, they're mainly aiming those ads at their own supporters in an effort to get them energized, enthusiastic, maybe angry, and ensure they get to the polls on Election Day," said Michael Hagen, associate professor of political science at Temple University.
But if the influence of political ads is small, why do campaigns spend so much?
"When you're talking about spending hundreds of millions of dollars ... multiplied by a very small effect, it can still add up to a kind of reasonable number of votes," Broockman explained.
The deciding votes in the 2024 presidential election could come from just a few thousand voters in one of the seven swing states, and that's who the campaigns are trying to reach with their ads.
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