On Thursday, Aug. 6, the 2016 presidential race will enter a new and important phase. Ten Republican presidential candidates will step on stage in a prime-time debate in Cleveland sponsored by Fox News and Facebook. The remaining GOP candidates will debate earlier that day. Viewership will be large, giving contenders their best opportunity so far to present their views, values and character to millions of Americans.

Although the event is advertised as a two-hour debate, the large number of candidates ensures that it will feel more like 10 simultaneous news conferences. After introductions, questions and commercials, each candidate will get roughly 10 minutes of speaking time, divided into answers of 1 minute and rebuttals of 30 seconds, plus a short closing statement. This translates into around seven questions per candidate.

So what to look for? In a debate like this, candidates must convey -- in word, tone and demeanor -- two or three things they want us to remember. If they don’t have a narrative or do a poor job of sharing it, that’s their fault, not the viewers’.

The moderators -- Fox News’s Bret Baier, Megyn Kelly and Chris Wallace -- will ask serious questions about consequential topics. Look for who is prepared and who isn’t. Glib only goes so far.

Click to read Karl Rove’s column in The Wall Street Journal.

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.