Round 1: Democrats to debate in Vegas

What happens in Vegas on Oct. 13 surely won't stay in Vegas. The first Democratic presidential primary debate will be held in the Nevada city and, if the audiences for the early Republican debates are indicators, 22 million people will be watching.

Hillary Clinton, Bernie Sanders, Martin O’Malley, Jim Webb and Lincoln Chafee will be on the stage for the two-hour debate.

And Joe Biden could join in the CNN-Facebook debate — the first of six on the Democratic side — even if he doesn’t enter the race until Oct. 13. Biden has met the minimum polling threshold set by CNN — averaging at least 1 percent in three polls despite not having declared his candidacy. So he would only need to file with the Federal Election Commission to participate.

Anderson Cooper of Anderson Cooper 360 will moderate, with CNN political correspondent Dana Bash and CNN español anchor Juan Carlos Lopez providing additional questions and anchor Don Lemon delivering questions submitted on Facebook.

Cooper last moderated a presidential debate in 2012.

The Democratic National Committee has sanctioned six presidential primary debates, four of them before the Iowa caucuses in February 2016.

At least two vice chairs of the national Democratic Party, along with House Minority Leader Nancy Pelosi, O’Malley and Sanders, have called for more debates. Clinton has said she’s open to more.

Party donors and activists also want more debates, including billionaire Tom Steyer, who has called for a forum to focus on climate change and the environment.

“Since the candidates — and the Democratic Party — understand that climate change is our greatest threat, they must allow voters the opportunity to hear a thoughtful and robust discussion — not just a single question — about their plans to solve this issue,” read a statement from Steyer’s NextGen Climate.

Meanwhile, GOP presidential candidates are preparing for a third debate on Oct. 28 in Boulder, Colorado. Since the second debate, the crowded field has narrowed by one with the abrupt departure of Wisconsin Gov. Scott Walker.

The remaining candidates face a set of possibly more stringent requirements for inclusion in round three — to be held by CNBC. Bobby Jindal, Lindsey Graham, George Pataki and Rick Santorum likely won’t make the cut. It is uncertain whether Rand Paul, John Kasich, Chris Christie and Mike Huckabee will participate. And, had Walker not suspended his campaign, he likely would have missed the cut.

Prime-time politics

The first Democratic presidential primary debate will be at 8 p.m. Central time on Oct. 13 on CNN, CNN en Español, CNN International and streamed on CNNgo. Westwood One will broadcast the debate on the radio.