Can the media stop politicians from misleading the public?

That’s the question on the minds of many journalists and commentators after Paul Ryan’s speech last night at the Republican National Convention, which continued the Romney campaign’s pattern of disingenuous and misleading attacks on President Obama. While Obama and his allies have made many misleading claims of their own, the frequency and repetition of the Romney campaign’s claims has been particularly striking.

The debate over the GOP ticket’s lack of responsiveness to factchecking first attracted widespread attention earlier this week after a pollster for Romney waved away criticism of a television ad falsely accusing President Obama of undermining work requirements for welfare. As Ben Smith reported in BuzzFeed:

The Washington Post’s “Fact Checker” awarded Romney’s ad “four Pinocchios,” a measure Romney pollster Neil Newhouse dismissed.

“Fact checkers come to this with their own sets of thoughts and beliefs, and we’re not going to let our campaign be dictated by fact checkers,” he said. The fact-checkers — whose institutional rise has been a feature of the cycle — have “jumped the shark,” he added after the panel.

The Romney crew has heavily featured the welfare ad, which strategist Ashley O’Connor called the campaign’s “most effective,” despite criticism from all three major fact-checkers. (Interestingly, Romney has previously cited these institutions’ work when it serves his purposes.) As of August 23, the welfare ad had run nearly 6,000 times. The chutzpah Ryan showed last night suggests that Romney’s campaign remains unbowed by the criticism it has faced.

This brazen disregard of pushback from journalists has brought on the latest episode in a recurring crisis of confidence among media types. Politicians have persisted in misleading claims before, but the ubiquity of online debunking in this cycle has brought the disjunction into sharper relief, as this chronology by NYU professor and media critic Jay Rosen highlights:

If we start back in the 1990s and read forward to the current campaign, we see distinct phases of innovation as political journalists react to misleading ads: first, the ad watch phase in the 90s; there was some mention of misleading elements, but the final tally was about effectiveness, or what I call “savvy.” The limitations of the ad watch led to direct fact-checking by the press, where actual grades are handed out. The emphasis is on judging truth and falsehood, not assessing effectiveness. So now we’re in a new phase: fact checking alone is not enough. The campaigns seem able to override it…

The Washington Post’s Dan Balz was similarly pessimistic two weeks ago:

News organizations instituted fact-checking and ad watches in reaction to earlier campaigns, when candidates were getting away with half-truths and worse, with little accountability. These have become robust and increasingly comprehensive. But they are not providing much of a check on the campaigns’ behavior.

This attention to the effectiveness of journalistic strategies is appropriate. In my view, though, we should rejoice that the inaccuracy of Romney’s ad is a continued topic of debate, not fall into despair or paralysis over the media’s failure to dictate the content of a presidential campaign. The underlying problem with these analyses is the misguided conclusion that factchecking is a failure if it does not eliminate deception. From a scientific perspective, however, factchecking is effective if it reduces the prevalence of misleading claims relative to an otherwise identical world that lacks factchecking, which seems likely to be the case (though we lack direct evidence on this point).

Brendan Nyhan is an assistant professor of government at Dartmouth College. He blogs at brendan-nyhan.com and tweets @BrendanNyhan.