Each presidential and vice presidential debate lasts 90 minutes. If you watch political ads, though, they may seem to go on much longer.
In the hours and days after the first presidential debate and this year's sole vice presidential version, both campaigns used debate footage in their ads — attempting to amplify messages, make counterarguments and drive the focus of the election.
Expect the same after tonight's presidential debate, the year's only town hall-style showdown, which is being held at New York's Hofstra University.
"The debate is the most recent thing the candidate has said directly to the nation," Stanford University professor Jon Krosnick says. "It's unfiltered, and I think it has particular news value."
Mitt Romney was seen as the clear winner in the first debate. Just a few hours after it ended, the Obama campaign released an ad, "Trust", which attacked him for his debate remarks about taxes. A few days later, the campaign released its "Big Bird" ad, which made a point about federal spending priorities that many Democrats say the president failed to seize upon.
"The idea that a candidate might want to respond to his opponent later in a way that didn't come to mind during the debate seems like a very positive use of the advertising opportunity," Krosnick says. (Sesame Workshop later asked the Obama campaign to stop airing the ad, saying: "We do not endorse candidates.")
The Romney campaign chose side-by-side footage from the debate for two of its ads, "Helping the Middle Class" and "Putting Jobs First." Both highlight a downcast-looking Obama as Romney criticizes his tax plan.
"A picture can tell a thousand words. So when you have one candidate triumphantly articulating a point and the other, through his body language, coming across as listless or otherwise unimpressive, that has the potential to convey a very strong message to viewers," says Costas Panagopoulos, associate professor of political science at Fordham University.
Another Romney campaign ad also draws attention to debate body language. The ad, "Fiscal Discipline," contrasts a laughing Vice President Joe Biden with Rep. Paul Ryan's sober assessment of the economy.
"This is really the only time on the campaign trail where you have both candidates in a room together reacting to each other directly," Panagopoulos says.
Debate footage can lend an impression of spontaneity to a candidate's words that cannot be duplicated in a stump speech or prepared remark, Panagopoulos says.
"One set of ads comes across as scripted or otherwise crafted by professionals and the other is really the candidates reacting to each other," he says. "I think the latter has a greater potential to be impactful."
Rollins College political science professor Rick Foglesong says post-debate ads can be powerful not just for the politicians, but also for voters, especially when the intent is to address factual disputes. While voters may not always seek out fact checkers independently, he says, the ads can bring those sources straight to their couches.
"I think there's something about the debates that causes a focus on style. The post-debate ads are an opportunity to refocus public opinion on substance," Foglesong says. "Of course it's substance in quotation marks because that's politically defined, but it's probably a good thing."