U.S. Senate36 out of the Senate’s 100 seats are up for election.

What’s at stake Democrats currently have a majority in the Senate, with 55 seats. Republicans can take control by winning 21 races in this election.

Potential runoffs In Georgia and Louisiana, if no candidate gets more than 50 percent of the votes Tuesday, the top two candidates move on to a runoff.

Wild card Greg Orman, the independent candidate in Kansas, hasn’t declared which party he will caucus with and could get to decide who holds the majority.

Ties in the Senate are broken by Vice President Joe Biden, a Democrat. Two independents, Sens. Bernie Sanders (Vt.) and Angus King (Maine), caucus with Democrats.

Arkansas

100% reporting

Tom Cotton 476,309 56.5%
Mark Pryor 332,669 39.5%

Colorado

99% reporting

Cory Gardner 965,974 48.5%
Mark Udall 916,245 46.0%

Georgia

100% reporting

David Perdue 1,355,392 53.0%
Michelle Nunn 1,154,388 45.1%
Amanda Swafford 48,930 1.9%

If no candidate gets more than 50 percent of the votes, the top two candidates will move on to a runoff on Jan. 6.

Iowa

100% reporting

Joni Ernst 586,921 52.2%
Bruce Braley 491,708 43.7%

Kansas

100% reporting

Pat Roberts 449,974 53.3%
Greg Orman 358,898 42.5%

Kentucky

100% reporting

Mitch McConnell 806,795 56.2%
Alison Lundergan Grimes 584,699 40.7%

Louisiana

100% reporting

Mary Landrieu 618,840 42.1%
Bill Cassidy 602,439 41.0%
Rob Maness 202,413 13.8%

This election is an “open primary.” If no candidate gets more than 50 percent of the votes, the top two candidates will move on to a runoff on Dec. 6.

New Hampshire

100% reporting

Jeanne Shaheen 250,722 51.6%
Scott Brown 234,846 48.4%

North Carolina

100% reporting

Thom Tillis 1,413,269 49.0%
Kay Hagan 1,364,758 47.3%

Virginia

99% reporting

Mark Warner 1,071,283 49.2%
Ed Gillespie 1,054,556 48.4%

Alabama

0% reporting

Jeff Sessions 0 0%

Alaska

100% reporting

Dan Sullivan 119,579 48.8%
Mark Begich 111,668 45.6%

Delaware

100% reporting

Christopher Coons 130,645 55.8%
Kevin Wade 98,819 42.2%

Hawaii special election

100% reporting

Brian Schatz 246,720 69.8%
Cam Cavasso 97,972 27.7%

Idaho

100% reporting

Jim Risch 285,322 65.3%
Nels Mitchell 151,697 34.7%

Illinois

99% reporting

Dick Durbin 1,850,862 53.1%
Jim Oberweis 1,503,942 43.1%

Maine

100% reporting

Susan Collins 411,211 68.4%
Shenna Bellows 189,653 31.6%

Massachusetts

100% reporting

Ed Markey 1,285,736 62.0%
Brian Herr 789,378 38.0%

Michigan

100% reporting

Gary Peters 1,693,781 54.6%
Terri Lynn Land 1,283,850 41.4%

Minnesota

100% reporting

Al Franken 1,052,794 53.2%
Mike McFadden 849,932 42.9%

Mississippi

100% reporting

Thad Cochran 370,208 60.4%
Travis Childers 228,974 37.4%

Montana

100% reporting

Steve Daines 210,863 57.9%
Amanda Curtis 145,601 40.0%

Nebraska

100% reporting

Ben Sasse 339,868 64.8%
Dave Domina 162,874 31.1%

New Jersey

99% reporting

Cory Booker 1,016,204 55.8%
Jeff Bell 772,991 42.4%

New Mexico

100% reporting

Tom Udall 280,074 55.4%
Allen Weh 225,706 44.6%

Oklahoma

100% reporting

Jim Inhofe 557,537 68.0%
Matt Silverstein 233,932 28.5%

Oklahoma special election

100% reporting

James Lankford 556,382 67.9%
Connie Johnson 237,531 29.0%

Oregon

94% reporting

Jeff Merkley 744,516 55.8%
Monica Wehby 498,191 37.3%

Rhode Island

99% reporting

Jack Reed 222,776 70.7%
Mark Zaccaria 92,389 29.3%

South Carolina

100% reporting

Lindsey Graham 665,605 54.5%
Brad Hutto 475,532 38.9%

South Carolina special election

100% reporting

Tim Scott 749,266 61.2%
Joyce Dickerson 454,279 37.1%

South Dakota

100% reporting

Mike Rounds 140,721 50.4%
Rick Weiland 82,408 29.5%
Larry Pressler 47,728 17.1%

Tennessee

100% reporting

Lamar Alexander 849,748 61.9%
Gordon Ball 437,175 31.8%

Texas

100% reporting

John Cornyn 2,855,068 61.6%
David Alameel 1,594,252 34.4%

West Virginia

100% reporting

Shelley Moore Capito 280,123 62.1%
Natalie Tennant 155,456 34.5%

Wyoming

100% reporting

Mike Enzi 119,534 72.3%
Charlie Hardy 29,043 17.6%
Sources: The Associated Press; secretaries of state and boards of election; Daily Kos; Ballotpedia; Natural Earth; U.S. Census Bureau
By Aaron Bycoffe, Jay Boice and Hilary Fung