Transcript for Democratic candidates focused on immigration as debate nears
Our Mary Bruce is in Miami tonight, where Democrats are debating for the first time. 20 of them. Let's get right to Mary tonight. You saw Elizabeth Warren on the day of this debate going to another center housing migrant children. Other candidates now following suit. Reporter: Yeah, David. We did see Elizabeth Warren out there, shining a spotlight on the immigration debate, as she gets ready to take center stage tonight. Other candidates are following her lead. Amy klobuchar was out there today. Over the next two days, we're going to see a steady stream of candidates dropping by, including, David, Bernie Sanders. I wanted to show everyone at home tonight just how big this democratic field is. 20 candidates facing off. And Mary, it's something we haven't seen before, in fact, they've had to make sort of alternate plans from what we usually see. Reporter: Yeah, David. Over two nights, ten candidates each night, all jockeying for attention. Tonight, Elizabeth Warren will be the one to watch. She has been rising in the polls. But tonight is also a chance for candidates like Cory booker and Beto O'rourke to try to breakaway from the pack. Tomorrow night, all eyes will be on Joe Biden and Bernie Sanders. One other person playing close attention, the president. He says he will be watching aboard air force one on his way to Japan. He says he will be watching, because he has to. David? The president watching tonight. Mary, thank you.
This transcript has been automatically generated and may not be 100% accurate.