How big an impact did Mitt Romney's performance in last week's debate have? Huge. Mr. Romney not only won the night, he changed the arc of the election—and perhaps its outcome. Surveys have him leading the RealClearPolitics average of polls for the first time since securing the GOP nomination in mid-April.
Prior to Oct. 3, Mr. Romney trailed President Barack Obama by an average of 3.1 points in national polls tallied by RealClearPolitics. Since the debate, Mr. Romney now leads Mr. Obama in the RCP average by a point, 48.2% to 47.2%, and the bounce is likely to grow. By comparison, Sen. John Kerry was widely seen to have bested President George W. Bush in the first 2004 debate (held on Sept. 30 of that year), but he never led in the RCP average in October.
In seven of the past nine presidential debate series, the challenger has gained more in the polls than the incumbent (or the candidate of the party in power). The first debate generally frames the series and establishes whether the bounce will be large or modest. Mr. Romney's bounce is significant.
It's unlikely that Mr. Obama will do as poorly next Tuesday at Hofstra University in New York. His supporters are demanding that he be more aggressive. He will be, telling AM radio's Tom Joyner on Wednesday that he'd been "too polite" in the first debate.
Karl Rove joined Fox News Channel as a political contributor in February 2008. He also currently serves as a columnist for the Wall Street Journal. Mr. Rove helped organize the political-action committee American Crossroads. His latest book is "The Triumph of William McKinley: Why the Election of 1896 Still Matters" (Simon & Schuster, 2015). Follow him on Twitter @KarlRove.