© 2014, Midwest Political Science Association. Does external monitoring improve democratic performance? Fact-checking has come to play an increasingly important role in political coverage in the United States, but some research suggests it may be ineffective at reducing public misperceptions about controversial issues. However, fact-checking might instead help improve political discourse by increasing the reputational costs or risks of spreading misinformation for political elites. To evaluate this deterrent hypothesis, we conducted a field experiment on a diverse group of state legislators from nine U.S. states in the months before the November 2012 election. In the experiment, a randomly assigned subset of state legislators was sent a series of letters about the risks to their reputation and electoral security if they were caught making questionable statements. The legislators who were sent these letters were substantially less likely to receive a negative fact-checking rating or to have their accuracy questioned publicly, suggesting that fact-checking can reduce inaccuracy when it poses a salient threat.