With experts giving Hillary Clinton a 71 percent chance of winning this election [1], Democrats are hopeful they can take back the Senate and the House of Representatives, too. Here's everything you need to know about the congressional battle.

The Race For the Senate

At the moment, the Senate race is much closer than the presidential election, causing many Republicans to focus on improving their odds down ballot [2] rather than campaigning for someone as contentious as Donald Trump [3]. Clinton's campaign also knows how crucial a Senate majority would be to her presidency, so many of her surrogates, including President Obama, have been concentrating [4] their efforts on these races as well.

Of the two sets of congressional elections, the Senate race is the one where Democrats have the best odds; FiveThirtyEight is giving them a 68 percent chance of winning this one [5]. Republicans currently hold a Senate majority, with 54 out of 100 seats. There are 34 seats up for grabs this year, 24 of which are held by Republicans. If Hillary Clinton wins the election, Democrats would need to net four additional seats to win the Senate because Tim Kaine, as vice president, would cast tie-breaking votes in a 50-50 party split Senate. If she loses, they would need to net five additional seats.

The Democrats have several paths to winning these five seats, while Republicans "need a near-perfect night to keep their majority [6]," according to NPR. Some of the states with a good chance of switching from red to blue include Wisconsin, Indiana, and Illinois (incumbent Senator Mark Kirk's latest comments about Tammy Duckworth aren't helping [7]). While the Senate candidates themselves always play the most important role in winning their own races, part of the problem for Republican Senate candidates is that their presidential nominee is dragging them down with him [8].

The Race For the House of Representatives

There is less data on the House race, but the chances of a Democrat victory are a lot slimmer by most accounts. All 435 seats are in play this election. At the moment, Republicans hold 247 seats and Democrats 188, so Democrats would need to gain 30 to seats to get a majority. "That requires sweeping nearly all Republican-held seats [9] in which they nurse even small hopes of winning," writes the Upshot.

Due to the intricacies of the current electoral map and redistricting [10], it's much harder to flip things around in the House of Representatives. Still, according to NPR, several game-changing districts in Florida could be flipped [11], along with districts in California, Nevada, and New York, among others.

With an election season as unpredictable as this one, there's still time for things to change before Nov. 8. But it looks like the congressional races are going to be the real nail-biters on election night.