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Do Political Ads Even Work?

2022 is set to be the most expensive midterm election in history. But the political science research is murky on how much that matters.

Luke Sharrett/Bloomberg/Getty Images
A bartender in Iowa watches Senator Ted Cruz on television in 2016.

For anyone living in a media market featuring contested political races—especially places such as Phoenix, Las Vegas, and Atlanta—these are the jackhammer months. Never in an off-year election have so many campaign spots been aired. TV spending will more than double from 2018 levels, according to estimates by the analytical firm AdImpact. The Wesleyan Media Project, which studies campaign commercials, calculated that more than two million ads had aired on broadcast television by early August—long before campaigns began their fall offensive.

Since most voters have been inundated with campaign ads their entire lives, there is a sense that Americans are sophisticated about them. We can all recognize attack ads with their grainy photos and voice-of-doom narration, as well as positive spots shot in close-up featuring the candidate walking the streets of the neighborhood where he or she grew up.

For all the public’s seeming knowledge about the campaign ad wars, there is a surprising number of misconceptions about the impact of TV spots. Much of what is considered orthodoxy in politics is based on unproven hunches and habit. Part of it is that political campaigns are not run as research experiments. You can’t run two campaigns—one the real one and the other a control group. No candidate will willingly stop spending on TV ads to test whether they are really effective.

Political science research has tried to fill in these gaps—and has done it somewhat successfully. But as the political science professors John Sides, Lynn Vavreck, and Christopher Warshaw concede in an article in the May issue of the American Political Science Review, “There are significant limitations to what we know about the effects of televised campaign advertising on election outcomes.” Still, while there is no certainty, there are important lessons for those who did not attend the recent political science convention in Montreal.

After watching a particularly devastating attack ad or a gauzy candidate bio, it’s easy to conclude that the spot will change the contours of the race. Not exactly. As Vavreck, who teaches at UCLA, put it in an interview, “There are no game-changers. That’s a truth that’s never wrong.” Vavreck is reflecting the political science consensus. There are so many ads that it is impossible to find evidence that any single spot—no matter how emotionally powerful—made a measurable difference in voter sentiment. When it comes to campaign spots, volume, not artistry, is what makes a difference.

Many academic studies of TV ads have focused on presidential races. But the effects of ads, while still small, are significantly larger in races that are not at the top of the ticket, such as a House election. Vavreck and her two co-authors used polling and other data to assess the potency of TV ads from 2000 to 2018. Their conclusion: “Despite increasing partisanship in the electorate, there are still persuadable voters that respond to television advertising—especially in down-ballot elections, where voters have less information about candidates.” As Vavreck summarized when we spoke, “The effects of advertising are small and go away quickly. But small does not mean inconsequential, especially in a close race.”

The study also came to the surprising conclusion, partly based on an analysis of voter files, that the limited power of TV ads lies mostly in the realm of changing perceptions of candidates rather than in motivating people to turn out. John Sides, who teaches at Vanderbilt and is a co-author of the study, told me, “If you want to mobilize voters, it’s much better to do it with personal contact than TV ads.”

It is a truism of politics that negative ads are more powerful than positive spots because they are mentioned more frequently in focus groups. Vavreck and her co-authors did not test the effectiveness of different types of ads. But Travis Ridout, a professor of political science at Washington State University and a co-director of the Wesleyan Advertising Project, said, “According to the best studies, negative ads are not more effective than positive ads.” Yale political scientist Alexander Coppock, who studies persuasion, is also dubious. “I have a low opinion of the focus-group approach,” he told me. “You don’t have to remember or like an ad for it to be effective. It can still work if you hate it.”

Coppock’s research on ads (some of which was conducted with Vavreck as a co-author) is experimental, often based on reactions to specific commercials. But he acknowledged the gaps in what is provable relating to TV ads as he admitted, “We are in the dark ages in doing experiments here.”

A prime example of uncertainty is whether in free-spending races there is a saturation point when an additional commercial fails to have any effect. It seems logical, but proving it is akin to finding the great white whale. “We didn’t find a point of diminishing returns,” Sides said, but he theorized that it probably exists. In the context of a campaign, there is always pressure to put more money on TV. Part of it is a competitive instinct and part of it, frankly, is that many consultants are paid on the basis of the size of the media buy. “Clearly, this is an industry where nobody knows what’s effective,” Coppock said. “And everyone involved says, ‘You have to do more.’”

There is widespread agreement among political scientists that the persuasive effects of a campaign ad last about as long as a box of chocolate chip cookies in a break room. But what is intriguing is the situation in Ohio where Democratic Senate candidate Tim Ryan dominated the airwaves over the summer while his GOP rival, J.D. Vance, did not air a single spot until August after winning a bruising May primary. Over a four-week period before Labor Day, Ryan aired 5,503 TV ads, according to the Wesleyan Media Project, dwarfing Vance’s modest buy. But will Ryan’s early advertising advantage matter in November? “I’m inclined to think that Ryan’s early advantage isn’t worth nothing,” Sides said, “but it’s not worth very much.” Ridout, however, makes the point, “We know from psychology that early impressions stick. And if you get the impression that Tim Ryan is a good guy fighting for the working class, it will take more negative ads to dislodge it.”

There are a few lessons from political science for campaign donors and ordinary voters. No matter how much a campaign hypes a particular ad in a fundraising email, the spot, at best, is only going to have a minuscule effect at the margins. And if you care about the effectiveness of your donation, ignore the high-profile Senate races that are dominating the news. You will get far more bang for your buck by investing in House races and down-ballot statewide contests for attorney general and secretary of state.

And most of all, don’t assume that campaign ad decisions are based on impeccable research. In truth, campaigns are flying blind just like the rest of us.