The 2018 election is here. Here are the races you should be watching

In just a few hours, polls will begin closing on Election Day 2018. Here are the races to pay especially close attention to this year:

NOTE: Poll closing times are included at the top of each entry. Politico has a complete list of poll closing times for all 50 states.

Senate

On Election Day morning, Republicans held 51 out of the 100 seats in the U.S. Senate. Democrats held 47, but two remaining seats belonged to Independents who caucused with the Democrats. If Republicans lose one of these seats, Vice President Mike Pence could still give Republicans a tie-breaker vote in his role as president of the Senate. If they lose two seats, then they would need at least one Democrat or Independent senator to vote with them in order to pass any legislation.

ARIZONA

Candidates: Rep. Martha McSally (R), Kyrsten Sinema (D)

This race is considered: A toss up (RealClearPolitics)

Polls close at 7 p.m. MST

This is the Senate seat formerly held by Sen. Jeff Flake (R-Ariz.), who is not seeking re-election. Arizona's other Senate seat, formerly held by the late Sen. John McCain (R-Ariz), is currently held by John Kyle , a former U.S. senator who was appointed by Arizona Gov. Doug Ducey (R) until a special election can be held in 2020. Kyle, who had previously been replaced in the Senate by Flake, has said that he will not run for re-election.

FLORIDA

Candidates: Sen. Bill Nelson (D) [incumbent], Gov. Rick Scott (R)

This race is considered: A toss up (RealClearPolitics)

Polls close at 7 pm EST for most of the state, but 7 pm CST for parts of the panhandle. 

Current Florida Gov. Rick Scott (R) is hoping to upset Democratic Sen. Bill Nelson. Nelson has been funding his campaign with his own substantial personal fortune, making it the single most expensive Senate race in Florida history. The latest RealClearPolitics average has Nelson up by 3.3 percent

Democrats are hoping to hold onto Nelson's seat as they try to gain a majority, while Republicans see it as a seat they could pick up to solidify their majority in case one of their other Senate seats flips.

INDIANA

Candidates: Sen. Joe Donnelly (D) [incumbent], Mike Braun (R)

This race is considered: a toss up (RealClearPolitics)

Polls close at 6 p.m. EST for most of the state, and 6 p.m. CST for some regions in western Indiana.

MISSISSIPPI

Candidates: Cindy Hyde-Smith (R) [incumbent], Mike Espy (D), Chris McDaniel (R)

This race is considered: Likely GOP (RealClearPolitics)

Polls close at 7 p.m. CST

Trump won Mississippi by 17.8 points (57.9 compared with 40.1 percent for Hillary). The state has come to be seen as reliably Republican, a drastic change from the 1930s when Republican presidential candidate Alf Landon won only 3 percent of the vote in the state.

But Mississippi also has an open primary, and the Republican incumbent is facing both Democratic and Republican challengers. In fact, Sen. Cindy Hyde-Smith is already asking her supporters to vote for her again in what she sees as a likely runoff election after this one. An NBC News/Marist poll on Oct. 18 showed Hyde-Smith with 38 percent of the vote among likely voters, and Republican challenger Chris McDaniel polling at 15 percent among the same group.

MISSOURI

Candidates: Sen. Claire McCaskill (D) [incumbent], Josh Hawley (R)

This race is considered: a toss up (RealClearPolitics)

Polls close at 7 p.m. CST

While Democrats hope to pick up at least two seats from Republicans, several seats of their own are in danger. In Missouri, challenger Josh Hawley is polling a negligible 0.6 points ahead, according to the RealClearPolitics average. Every poll taken throughout the year has shown the two candidates to be within 4 points or less.

MONTANA

Candidates: Sen. Jon Tester (D) [incumbent], Matt Rosendale (R)

This race is considered: a toss up (RealClearPolitics)

Polls close at: 8 p.m. MST

Like with McCaskill in Missouri, Sen. Jon Tester (D-Mont.) is in a fight to keep his seat from widening the current GOP majority in the Senate. Tester has managed to hold the lead in every major poll taken of his race so far this year, but a poll by the Trafalgar Group taken Nov. 2-5 showed him with a slim 1 percentage point advantage.

NEVADA

Candidates: Sen. Dean Heller (R) [incumbent], Rep. Jacky Rosen (D)

This race is considered: a toss up (RealClearPolitics)

Polls close at 7 p.m. PST

An Emerson College poll released on Monday showed Rosen leading Heller 49 percent to 45 percent, just outside the poll's margin of error of +/- 3 percent.

NORTH DAKOTA

Candidates: Sen. Heidi Heitkamp (D) [incumbent], Kevin Cramer (R)

This race is considered: Leans GOP (RealClearPolitics)

Polls close at 7 p.m. CST

Heitkamp is one of the most endangered Democratic incumbent senators this year. She came out strongly against Supreme Court Justice Brett Kavanaugh's nomination, after a poll from early October showed Cramer with a 10-point lead over Heitkamp. Cramer seems to have kept that lead, and the RealClearPolitics average still puts him up by 9 percentage points.

TENNESSEE

Candidates: Sen. Marsha Blackburn (R) [incumbent], former Gov. Phil Bredesen (D)

This race is considered: A toss up (RealClearPolitics)

Polls close at 8 p.m. EST

Sen. Marsha Blackburn (R-Tenn.) was up 8 points in an Emerson College poll released on Nov. 1, despite Bredesen snagging a celebrity endorsement from pop star Taylor Swift.

TEXAS

Candidates: Sen. Ted Cruz (R) [incumbent], Rep. Beto O'Rourke (D)

This race is considered: Leans GOP (RealClearPolitics)

Polls close at 7 p.m. CST for most of the state, and 7 p.m. MST for parts of west Texas.

Rep. Beto O'Rourke  is seeking to take a Republican Senate seat away from Sen. Ted Cruz (R-Texas). While this race has garnered national attention, Beto has been unable to move this race into the toss up category. A poll taken Nov. 3-5 by the Trafalgar Group shows Cruz with a 9-point lead.

WEST VIRGINIA

Candidates: Sen. Joe Manchin (D) [incumbent], Attorney General Patrick Morrisey (R)

This race is considered: a toss up (RealClearPolitics)

Polls close at 7:30 p.m. EST

Manchin holds a 5-point lead over Morrisey, according to an Emerson poll that ended on Oct. 31, but a loss for the GOP candidate in this race might not be a total loss for the GOP. Even though he's a Democratic senator, Manchin votes with President Donald Trump's agenda 60 percent of the time.

The House of Representatives

In the House of Representatives, 75 seats are currently considered to be highly competitive. Democrats need to hold onto all of their seats and gain 23 additional seats in order to gain a majority. At least 17 seats currently held by the GOP are considered to be leaning Democrat.

In the House, 30 races are currently considered to be toss ups: California districts 10, 25, 39, 45, and 48; Florida 15 and 26; Georgia 6; Illinois 14; Iowa 3; Kansas 2; Kentucky 6; Maine 2; Missouri 8; Minnesota 1; New Jersey 3 and 7; New Mexico 2; New York 19 and 22; North Carolina 9 and 13; Ohio 12; Pennsylvania 1 and 10; Texas 7 and 32; Utah 4; and Virginia districts 2 and 7.

Governor races

ALASKA

Candidates: Mike Dunleavy (R), Mark Begich (D)

This race is considered: a toss up (RealClearPolitics)

Polls close at 8 p.m. AST for most of the state and 8 p.m. HST parts of the Aleutian Islands

Incumbent Gov. Bill Walker (I) decided to suspend his campaign on Oct. 19, after struggling in the polls. Walker threw his support behind former Sen. Mark Begich, arguing that Begich had a better chance of defeating Republican Mike Dunleavy.

FLORIDA

Candidates: Mayor Andrew Gillum (D), Rep. Ron DeSantis (R)

This race is considered: a toss up (RealClearPolitics)

Polls close at 7 pm EST for most of the state, but 7 pm CST for parts of the panhandle. 

Democratic Tallahassee Mayor Andrew Gillum and Republican congressman Rep. Ron DeSantis (R-Fla.) are running for the seat soon to be vacated by term-limited current Gov.  Rick Scott.

NEVADA

Candidates: Adam Laxalt (R), Steve Sisolak (D)

This race is considered: a toss up (RealClearPolitics)

Polls close at 7 p.m. PST

This is one of the tightest gubernatorial races in the country, with neither candidate polling with more than a 2 percentage point lead all year. The latest Emerson College poll, released on Monday, showed Sisolak with a 1 percentage point lead, well within the margin of error of +/- 3 points.