Republican presidential nominee Donald Trump and Democratic presidential nominee Hillary Clinton spoke during their presidential town hall debate at Washington University in St. Louis, Missouri, Oct. 9, 2016. Reuters

With the presidential election less than three weeks away, Democratic nominee Hillary Clinton and Republican nominee Donald Trump are scheduled to take the debate stage at the University of Nevada, Las Vegas’ Thomas & Mack Center Wednesday night for their final face-to-face showdown.

Clinton was leading Trump in national polls in a two-way matchup by an average margin of 6.6 percentage points, according to RealClearPolitics. Will Trump seize the opportunity to close the gap with his opponent, or will Clinton widen her lead? Here’s what you know to know to tune in Wednesday night.

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When is the debate? Clinton and Trump will enter the stage at 9 p.m. EDT and are scheduled to finish at 10:30 p.m. EDT. For each of the debate’s six topics, the candidates will have 15 minutes to discuss, starting with one nominee answering a question from the moderator and the other presenting his or her response.

Where can I watch? All of the major broadcast networks — ABC, CBS, FOX, NBC, CNN, Fox News, MSNBC, and C-SPAN, among others — will be showing the debate live, but those watching on laptops have options as well. The Washington Post, New York Times and several broadcasters will be live-streaming the event. YouTube has provided a list of who’s showing the debate online, along with media groups reporting on the ground in Las Vegas.

Who is the moderator? Chris Wallace, a “Fox News Sunday” host, has a reputation for challenging Republicans and Democrats alike. The first anchor from Fox to host a general election debate, Wallace pledged to offer viewers a “fair and balanced” discussion with the two nominees on Wednesday. Wallace, who has moderated GOP primary debates with colleagues Megyn Kelly and Bret Baier, told his employer Tuesday, "If people say, 'it was a great debate and I don’t remember you being there,' I will have done my job."

What are the topics? Wallace’s six debate topics, as told to Fox News, include immigration, the economy, the Supreme Court, “debt and entitlements,” “foreign hot spots” and “fitness to be president.” Lester Holt’s selection of talking points for the first debate, by comparison, featured “America’s direction,” “achieving prosperity” and “securing America.”

Was Gary Johnson invited? Because the Libertarian Party nominee's polling was below 7 percent less than a week before the debate — well below the required 15 percent — the former New Mexico governor was not invited to the final debate. Green Party nominee Jill Stein, who has polling averages far below Johnson’s, also didn’t make the cut.

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