Democrats prepare for showdown at first debate in Vegas

LAS VEGAS -- The Republicans have had two go-arounds. Now it's the Democrats' turn. We are less than a day away from the first democratic debate. And there's been no shortage of buzz. Hillary Clinton arrived in Las Vegas late Monday afternoon with husband Bill Clinton in tow.

Vegas has been the site of many legendary prize fights. And Tuesday night, it's round one for the Democratic presidential contenders

Front and center for their first debate is frontrunner Hillary Clinton. To her right, Vermont Senator Bernie Sanders, who keeps inching up in the polls.

It's a high stakes showdown and an opportunity for Clinton's rivals to go after her, head to head, on the issues that are hurting her in the polls.

President Barack Obama weighed in on the ongoing controversy over her personal email server in an interview on CBS' 60 minutes.

"She made a mistake, she has acknowledged it," he said.

But looming large over the Democratic field is of course Vice President Joe Biden. Sources tell ABC News he will announce his campaign plans this week.

Biden spent the weekend in Delaware with family, but gave no hints of his plans to reporters.

The president said he'll let Biden make his own decision, but had big praise for his number two.

"I think Joe will go down as one of the finest vice presidents in history," Obama said. "And one of the more consequential. I think he has done great work."

Donald Trump said Monday in New Hampshire he's tuning in to Tuesday night's debate, but also got in a dig at the Democratic field.

"It's gonna be hard to watch," he said. "I think it's not gonna be a very exciting debate."

The first two Republican presidential debates had record television ratings. The Democrats are getting a much later start. But with just five candidates on stage, they'll have more opportunities to break through.

And if Biden decides to join the race, CNN still has an empty sixth podium waiting for him in Vegas.

Two new CNN/ORC polls show Clinton with commanding leads in two early voting states. The former secretary of state has a 22 point lead over Sanders in Nevada. The lead stands at 16 points with Biden.

In South Carolina, Clinton leads Sanders by 50 points. If Biden is factored in, she leads the vice president by 25 points and Sanders by 31.

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