美国有线新闻 CNN 美国国会将换届选举 驴象之争再度上演（在线收听）

Tonight is the last of three head-to-head debates between Republican presidential nominee Donald Trump and Democratic presidential nominee Hillary Clinton. It's scheduled to start at 9:00 p.m. Eastern at the University of Nevada Las Vegas. You can watch it live on CNN.

This debate will have the same format as the first one, with the two candidates taking questions from a moderator. And for this event, that moderator will be a FOX News anchor named Chris Wallace.

But keep in mind, it's not just president that Americans will be voting for on November 8th. All 435 voting members of the U.S. House of Representatives will be chosen, as they are every two years. In the 100- member Senate, about a third of the seats will be determined. Senate terms are for six years.

Currently, Republicans control both chambers of Congress. But just like the uncertainty surrounding the presidential election itself, there's uncertainty over who control Congress after the election.

REPORTER: For the Senate, the math is complicated. Right now, the Senate has 54 Republicans, 44 Democrats and two independents. Thirty-four senators are up for reelection this year.

Here's a thing you need to remember and Republicans wish they could forget: Democrats only need to gain five seats to gain control of the Senate. They face a more difficult battle, though, in the House of Representatives. Democrats need to gain 30 seats to win back the majority there. It's a high hurdle with relatively few competitive districts. But House Minority Nancy Pelosi said that if the election were held this week, Democrats would regain control of the House.

Republicans disagree. Still, Speaker of the House Paul Ryan told Republican donors that Trump's numbers are worse than John McCain's were in 2008. 2008 is the year that Democrats did indeed win back the House of Representatives and Pelosi was speaker of the House. They held control for the first two years of Barack Obama's presidency.

Why are the House and Senate so important? Well, first, they share responsibility for creating and passing the country's laws. Second, Senate confirms or rejects the president's nominees to the Supreme Court.