"That's what's driving a lot of this — the realization that negative advertising works," Loevy said. "These people would not say they're lying, but we all know they're stretching the truth, taking things out of context ... The more extreme, the better."
Does the truth matter? Willem DeVries, a philosophy professor at the University of New Hampshire, argues that it does.
"To the extent that elections are supposed to settle policy issues... truth (that is, real honest-to-goodness truth, not 'truthiness') should matter, because decisions made on the basis of falsehoods tend to be bad decisions," he wrote in an email. "If you think that democracy really means that good policy is supposed to emerge from the wisdom of an informed electorate, then a campaign riddled with falsehoods is an abrogation of democracy."
Problems arise, DeVries said, when campaigns opt for emotional appeals or psychological manipulation regardless of the truth. "There can be a race to the bottom," he wrote, "for such techniques have proven themselves often highly effective."
His fellow UNH philosophy professor, Nick Smith, wonders if the American public is to blame for not calling out politicians when they do lie or deceive.
"Perhaps we do not hold them accountable because we have become so biased toward our own views that we view political discourse as a kind of ideological warfare where any weapon should be deployed," Smith said. "So if a politician gets caught in a lie, some do not see this as a character defect but rather an occupational hazard."
McPherson, the Tufts professor, suggests that a politician in office — including Obama as sitting president — should be held to higher standards of truth than a candidate seeking to gain office. "Challengers are desperate," McPherson said. "Who knows what desperate people will do?"
During the past week, both presidential campaigns have accused the other of wallowing in lies and deception. It has been a prominent theme in speeches at the Democratic National Convention.
"Tonight I want to talk to you about a scary subject for many, many Republicans," Illinois Gov. Pat Quinn said Tuesday. "I want to talk about facts."
He went on to assail the GOP claims, widely debunked by independent fact-checkers, that Obama was weakening the work requirement of federal welfare policy. The Romney campaign responded with a press release citing an assortment of independent fact-checkers who found fault with statements by various Democratic speakers.
On Wednesday, Democratic National Committee Vice Chairman R.T. Rybak took aim at Ryan's credibility, saying he has had "an increasingly exposed history of exaggerating or fabricating the truth."
"We can't have a person a heartbeat away from the president who can't look people in the eye and tell them the truth," said Rybak, the mayor of Minneapolis.
PolitiFact's Adair says both campaigns seem ready to push the boundaries on accuracy. "It's a classic strategy: Don't let the facts get in the way of a good campaign theme," he said. And even when evidence might be sketchy, "Both campaigns have certain story lines they're going to push."
Follow AP National Writer David Crary on Twitter at http://twitter.com/CraryAP