The Republican presidential candidates, including a surging Newt Gingrich and a suddenly defensive Mitt Romney, will debate Saturday night at Drake University in Des Moines as the days tick down to the Jan. 3 Iowa caucuses.

The 9 p.m. ET debate is sponsored by ABC News, WOI-DTV (the Des Moines ABC News affiliate), Yahoo!, the Des Moines Register and the Republican Party of Iowa. Here are the full details:

Where can I watch the debate?

ABC will broadcast the entire debate with coverage beginning at 8:30 p.m. ET. ABCNews.com, Yahoo.com, MyABC5.com and DesMoinesRegister.com will live-cast the debate.

As usual, the Fix will live-blog the entire debate starting at 8:30 p.m.

Who is participating?

Minnesota Rep. Michele Bachmann, former House Speaker Newt Gingrich (Ga.), Texas Rep. Ron Paul, Texas Gov. Rick Perry, former Massachusetts governor Mitt Romney and former U.S. senator Rick Santorum (Pa.).

Who will moderate the debate?

ABC’s Diane Sawyer and George Stephanopoulos will moderate the forum.

What is the format?

The debate will be two hours long and with only six candidates on stage, Yahoo! News Washington bureau chief David Chalian called it a ”much more intimate affair” than previous debates have been.

The sponsors will poll viewers throughout the debate using an app called IntoNow. They will use poll data and viewer feedback to frame follow-up questions in the debate, Social Beat reported.

What is the official hashtag?

ABC recommends the hashtag #IowaDebate.

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