Four things to watch for in the debate

1. How far can candidates go in challenging Donald Trump? Will rivals demand he explain his branding of undocumented Mexican immigrants as criminals and rapists? And what will it cost them?

2. Will Trump evolve from showman to potential president? While he’s comfortably ahead in most polls, Trump’s negatives are also huge. This week, Trump posted a Facebook video saying he wanted rivals to answer one question: “How will you make America great again?” Trump needs to answer that himself.

3. Is it time for a new generation? Florida Sen. Marco Rubio, 44, and Scott Walker, 47, the governor of Wisconsin, are the year’s biggest curiosities. Each boasts a strong political résumé and plenty of campaign cash. The public, though, barely knows them. Ask yourself: Would I feel better handing the reins to a new generation or more scared?

4. Who is the next big thing? Trump could fade. Jeb Bush already could be maxed out. Underdogs often intrigue voters, and it doesn’t take much to make an unknown an overnight trending topic. Watch Chris Christie and John Kasich.

This story was originally published August 6, 2015 at 2:00 AM with the headline "Four things to watch for in the debate."