Do Campaign TV Ads Really Change Voters' Minds?

updated political "daisy" ad — This 2003 political TV ad by the political action group MoveOn.org alluded to the famous 1964 Lyndon B. Johnson presidential campaign ad that warned against nuclear war. The updated ad asked the U.S. government to "let the inspections work" referring to United Nations weapons inspections currently underway in Iraq. MoveOn.org/Getty Images

The 2022 midterm elections are fast approaching and if you live in a state with a hotly contested race, you're probably being blasted by political TV ads. By late September, campaigns across the United States had already spent more than $6.4 billion on ads (TV, print and online), and are expected to spend a total of $9.7 billion by Election Day in November, far more than both the 2018 and 2020 elections.

This year's record spending on TV and other types of political ads reflects the "high stakes" of the 2022 midterms, says Christopher Warshaw, a political science professor at George Washington University. The Senate is split 50-50 and the Democrats hold the House of Representatives by a slim nine-seat majority.

"Campaigns hope that by buying a few extra thousand ads they can put their candidates over the top and win control of the government for their party," says Warshaw, who published a study in 2022 in American Political Science Review, with two other researchers, on the effectiveness of political TV ads. "The American public is more polarized than ever before, but there's still this swath of independent voters in the middle who are trying to decide."

And political ads, despite how annoying and even stressful they can be, have proven effective, especially in the tightest races. Even a bombardment of ads doesn't necessarily turn people off. The study authors found "only modest evidence that the 1,000th ad is less effective than the 10th," according to their Washington Post article.

TV Ads May Be More Effective for 'Down Ballot' Races

The 2016 presidential election was decided by razor-thin margins of victory for Republican candidate Donald Trump in battleground states like Michigan, Pennsylvania and Wisconsin. In 2020, Joe Biden and the Democrats spent heavily on political TV ads in those same battleground markets.

As Election Day 2020 approached, pro-Biden TV ads outnumbered pro-Trump ads by 5,301 in key markets like Harrisburg, Pennsylvania, and by 4,291 in Green Bay, Wisconsin, from Sept. 5 to Oct. 11, 2020.

In their research, Warshaw and his colleagues estimated that for every additional 1,000 TV ads a campaign runs compared to its opponent, it can capture 0.2 percentage points more of the vote. And the results of the 2020 presidential seemed to bear this out.

In 2016, Trump won Wisconsin's 10 electoral votes by about 0.7 percent, but in 2020, Biden won Wisconsin by 0.7 percent. The same swing happened in Pennsylvania. In 2016, Trump won Pennsylvania's 20 electoral votes by 0.7 percent, but in 2020, Biden won the state by 1.2 percent.

For their study on the effectiveness of political TV ads, Warshaw and his co-authors — John Sides at Vanderbilt University and Lynn Vavreck at UCLA — analyzed data from more than 2,250 US elections from 2000 through 2016, not just presidential races.

What they found was that TV ads had a much greater effect on "down ballot" races compared to presidential contests: three times greater for Senate races; four times greater for gubernatorial races; and 12 times greater for the really obscure races like state treasurer.

The reason, says Warshaw, is that the whole function of political TV ads is to convey some sort of new information to the voter.

"At the presidential level, ads don't give you much new information that you didn't already have," says Warshaw. "We already knew so much about Donald Trump and Joe Biden and Barack Obama. Whereas the races for the House, or governor or Senate, people are following those a lot less closely. Voters might not know anything about those candidates beyond their party affiliation."

For that target demographic of undecided "swing" voters, any new information provided by a TV ad about a state or local race could swing them in the campaign's desired direction.

Moving the Needle One Percentage Point

Many studies have been done on the effectiveness of political TV ads and shown mixed results. Some studies have determined that these ads have limited persuasive power. Other studies have shown that it is the nature of ads that is the issue: positive versus negative.

While Warshaw didn't look at the content of ads in his study, he did point us to another study that showed all types of ads — positive, negative, partisan, non-partisan — seemed to have the same small effect on voting outcomes. But in the game of TV ads, the point is not to convince a registered Democrat to vote for the Republican candidate – it's to speak to the independent voters.

Warshaw reiterates that his research showed a very small effect of TV ads on influencing people to vote for a certain candidate, with the largest "plausible" effect being one to two percentage points. So, if he was consulting a campaign on how to spend its money, he wouldn't automatically recommend pouring millions of dollars into TV ads.

"If you're a Republican candidate, you're not going to win here in Maryland where I live with TV ads," says Warshaw. "It doesn't matter how many ads you run. Likewise, a Democrat is not going to win in Utah or Idaho by grabbing one or two additional percentage points with TV ads."

But as we saw in the last two presidential races, there are plenty of contests that have been decided by less than one percentage point. Warshaw says this is also a lesson for political donors who want the most bang for their buck. A donation to a presidential campaign is a drop in the bucket, but that same donation to a down ballot race could buy more ads that actually influence the outcome.

The Future of Political TV Ads in the Streaming Age

Research like Warshaw's looked at data from 2000 to 2016, a time when most American voters watched hours of cable television every day. Between 2016 and 2021, though, a quarter of all cable TV subscribers "cut the cord" and switched to streaming, and Insider Intelligence projects that fewer than half of all American households will have cable TV subscriptions by 2023.

"I still think TV ads matter, but maybe they matter a little bit less projecting into the future," says Warshaw.

Digital ads, like the political ads you might see on Facebook or before a YouTube video, have been found to have an even smaller effect on voters, but political advertisers are getting smarter. Now, on ad-supported streaming TV channels like Lifetime and Vice, campaigns can run hyper-targeted ads based on the subscriber's personal data.

As The New York Times put it, "Next door neighbors streaming the same true crime show on the same streaming service may now be shown different political ads — based on data about their voting record, party affiliation, age, gender, race or ethnicity, estimated home value, shopping habits or views on gun control."

You can run from political ads, but you can't hide.