In Tuesday night’s vice-presidential debate, Sen. Tim Kaine was rude, boorish and hectoring. Gov. Mike Pence dominated with his humble, polite demeanor, command of facts and Midwestern common sense. Donald Trump needs to match that performance in his debate Sunday with Hillary Clinton.

Mr. Trump needs a win in part to offset his disadvantage in one of the election’s most important activities: get-out-the-vote efforts. Democrats have opened more field offices, deployed far more organizers, and coordinated between Hillary Clinton’s campaign and the party.

Mr. Trump has shown little interest in this, content to leave the turnout operation to the Republican National Committee. The RNC is doing great things, but its work would have been more effective if Mr. Trump had made this a campaign priority. All of those new faces at Mr. Trump’s many rallies during the past 16 months should have been systematically recruited, trained and deployed into a massive GOP ground game.

If Democrats have a bigger and better-organized effort, it could prove decisive. Consider 2012. The day before the election, President Obama was ahead of Mitt Romney by only 0.7% in the Real Clear Politics average of polls. Yet Mr. Obama won the popular vote by 3.9%.

To continue reading Mr. Rove's column in the Wall Street Journal, click here.

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.