12 things to know about tonight's Republican debate

What time: The first part of the debate begins at 6 p.m. (ET); the "primetime" debate starts at 8:30 p.m.

Hosted by: CNN and Facebook

Airs on: The debate will air live on CNN, CNN International and CNN en Español. The Salem Radio Network will air the debate live through their broadcast radio stations across the country. Check  your local listings.  CNN is on: DirecTV - channel 202; Dish Network - channel 200; ATT U-verse - channel 202

Live stream: CNN will live stream the debate on CNN.com's homepage and across mobile platforms from 5 p.m. to 11 p.m. ET. According to CNN, all users will be able to watch live CNN TV online and on their mobile devices without logging in.

Moderators: The debate will be moderated by Wolf Blitzer, with CNN's Dana Bash and  Salem Radio Network talk show host Hugh Hewitt asking questions.

Who can participate: For the 8:30 p.m. primetime debate, CNN used early-state polls to determine who is on the main stage.  Those candidates met one of three criteria: an average of at least 3.5 percent nationally; at least 4  percent in Iowa; or at least 4 percent in New Hampshire. The polls considered were conducted between Oct. 29 and Dec. 13.

Here are the candidates participating in the primetime debate, their poll number percentage (from CNN’s Poll of Polls) and their websites.

Where they will stand:

Donald Trump will stand center-stage for the debate. To Trump’s right will be Carson, Rubio, Fiorina and Kasich. To his left will be Cruz, Bush, Christie and Paul.

Who is in the 6 p.m. debate

Where they stand

From left to right, Pataki, Huckabee, Santorum and Graham.

Likely issues

While we don't know for sure, the likely issues to be raised in the debate include:

When's the next one

The sixth Republican debate will be held Thursday, Jan. 14, in Charleston, S.C. It will be hosted by the Fox Business Network.

The next Democratic debate will be in Manchester, N.H., on Saturday, Dec. 19. It will be hosted by ABC News and WMUR.