Transcript for Sanders prepares to meet Bloomberg on debate stage
Next, to the race for 2020 tonight, and former mayor Mike Bloomberg, rising in the polls. He will be on the debate stage this week. The other candidates preparing to take aim. They have said he's trying to buy the presidency. We do have breaking developments in this tonight. What Bloomberg is now promising to do if elected. ABC's Eva pilgrim on the campaign trail in Nevada tonight. Reporter: 24 hours before Michael Bloomberg takes the debate stage for the first time in this race, Bernie Sanders sounds ready to rumble. Here is the message -- anybody here worth $60 billion, you can run for president! And you can buy the airwaves! My friends, that is called oligarchy, not democracy. Reporter: Bloomberg's campaign manager says the democratic primary is now a two-man race. The billionaire, former New York mayor versus the self-described democratic socialist senator. That doesn't sit well with Pete buttigieg, who came out of Iowa and New Hampshire riding high. We're asking people to choose between a revolution and the billionaire who thinks you can just buy your way onto television and win that way. Reporter: Later, I pressed the former South Bend mayor. Do you think he's buying the race or do you think he's just trying to beat Donald Trump? No, he's definitely trying to buy the race. But here's the thing -- it's not that simple. You have to actually be willing to look voters in the eye, to take questions. At some point, you've got to be ready to be challenged. Reporter: Bloomberg's rivals making it clear that tomorrow night, the gloves come off. This is about our values. What kind of a nation we want to be? Reporter: Elizabeth Warren tweeting -- "At least now primary voters curious about how each candidate will take on Donald Trump can get a live demonstration of how we take on an egomaniac billionaire." Eva with us now. And Michael Bloomberg hasn't been on the debate stage since 2009. He's prepping with his team. But you learned some breaking news just before we came on the air tonight about a new promise from Bloomberg, should he get elected? Reporter: That's right, David. We are just learning Bloomberg's campaign saying that if he is elected president, he will immediately put his company into a blind trust and then sell it. He knows his wealth will be an issue on the debate stage tomorrow night and they are trying to get ahead of it. David? All right, Eva pilgrim, thank you.
This transcript has been automatically generated and may not be 100% accurate.