EXCLUSIVE PICS: Behind the Scenes Before the Fox News GOP Debate

Everything You Need to Know About Tonight's Fox News GOP Debate

We're just hours away from the Fox News GOP debate you've been waiting for! 

Shannon Bream caught up with Bret Baier, who will moderate alongside Megyn Kelly and Chris Wallace, to get some of his last-minute thoughts. 

Baier said the moderators will be trying to keep the debate from going "off the rails" with personal attacks between the candidates. 

"It's going to be, ideally, fiery but substantive," said Baier, adding that this will be "different" from previous debates. 

He also said he's looking forward to seeing the candidates get into deeper policy discussions, since the field is down to four: Donald Trump, Marco Rubio, Ted Cruz and John Kasich. 

"There's a fine line between letting it breathe and letting it go off the rails. We'd like to somehow find that sweet spot."

Watch more from Bret above.

The must-see event starts at 9:00pm ET at Detroit's historic Fox Theatre. 

Follow Fox News on Facebook during the debate to see more from Shannon, as she talks to the moderators during the breaks.