Democrats currently hold a one seat majority in the United States Senate with Vice-President Harris often acting as the tie-breaking vote. However, Republicans have the potential to take over the majority on Election Day. Here are the key races to watch that could change the makeup of the Senate.

Arizona 

Arizona became a toss-up when incumbent Krysten Sinema, who switched her party affiliation from Democrat to Independent last year, announced she would not be running for reelection. The race is now a battle royale between Rep. Ruben Gallego (D-Arizona 3rd) and Kari Lake, who gained name recognition during the Arizona gubernatorial race in 2022.

Maryland 

Former Governor Larry Hogan (R) is making this Senate race competitive in normally deep-blue Maryland. Hogan maintained high levels of popularity throughout his term in office due to his perceived commonsense and moderate policy stances. His opponent is Democrat Angela Alsobrooks, the executive of Prince George’s County. Hogan has a tough road to victory though – he’ll need a majority of voters to split their ticket by voting for him and Democratic presidential nominee Kamala Harris.

Michigan 

Rep. Elissa Slotkin (D-Michigan 7th) and Mike Rogers are battling over retiring Democratic Senator Debbie Stabenow’s seat. Rogers is a former FBI special agent and served as the Representative for Michigan’s 8th District from 2001-2015. In recent weeks, Slotkin has been encouraging voters to split their ticket by voting for the Republican presidential candidate and herself, the Democrat senate candidate, a nod to former President Trump’s popularity in the state.

Montana 

 Sen. Jon Tester (D-Montana) is considered to be the most vulnerable incumbent running for reelection this year. Tester has proven himself to be a savvy politician and has big name recognition, but in his last election, he was not running at the same time as President Trump, who won the state in 2020 by 16 points over President Biden. Tester’s opponent, Tim Sheehy, is a former Navy Seal with President Trump’s endorsement and enough wealth to finance his campaign. Sheehy is projected to win this seat easily, guaranteeing a new Senate seat for the Republicans.

Nevada 

The transient nature of Nevada’s population makes it a seemingly perpetual swing state with tight margins. As evidence of this, the race between Sen. Catherine Cortez Masto (D) and Adam Laxalt (R) was the closest in the nation in 2022. This time around, incumbent Jacky Rosen (D-Nevada) is seeking her second term in the Senate. Her Republican challenger is Sam Brown, a retired Army veteran who suffered third-degree burns from a roadside bomb explosion in Afghanistan. Brown is running as an outsider and cultural conservative. Interesting to note is that Nevada is one of several states that also has a pro-abortion measure on the ballot which could affect who gets more votes in the Senate race.

Ohio 

Like Tester in Montana, Sherrod Brown (D-Ohio) is another incumbent defending his seat in a conservative-leaning state. Once seen as a bellwether for national elections, Ohio has only elected one Democrat for statewide office since 2012 – Sherrod Brown. That is an impressive feat that tells a lot about Brown’s political skills. His Republican opponent is Bernie Moreno, a Colombian immigrant turned wealthy American businessman. Moreno may benefit from having Ohio’s other senator, J.D. Vance, on the ticket for Vice President.

Pennsylvania 

Pennsylvania is no stranger to being an election year battleground, and 2024 is no exception. As the site of the first assassination attempt on President Trump, Pennsylvania has seen some of the most pivotal moments of this campaign cycle. How those events will affect the senate race remain to be seen. Democratic Sen. Bob Casey has held the seat since 2007 and is generally viewed as a moderate who reaches across the aisle. His opponent is Dave McCormick, a former Hedge fund manager and West Point graduate. Going into Election Day, this race is statistically tied.

Texas  

This is the only Senate race this year in which an incumbent Republican has a chance of losing his seat. Although the Democrats tried to unseat longtime Sen. Ted Cruz six years ago with Beto O’Rourke, they believe that Rep. Colin Allred (D-TX 32nd) can perform better with minorities than O’Rourke did. Texas has become a competitive state thanks to the influx of new voters in recent years from states like California. However, the state has voted largely for Trump in the past and if it does so again, it’s unlikely that Cruz will lose.

Wisconsin 

Sen. Tammy Baldwin is running for her second term against venture capitalist Eric Hvode. Baldwin has been focusing on Hvode’s business ties in California. Hvode has attacked Baldwin’s partner, Maria Brisbane, for profiting off industries that Baldwin oversees as chair of the Senate Appropriations Subcommittee on Labor, Health and Human Services, and Education. Wisconsin is historically a swing state, voting for Trump in 2016 but switching to Biden in 2020. This senate race will likely come down to the wire.

West Virginia 

Longtime West Virginia Senator Joe Manchin is retiring, putting his seat up for grabs for the first time in decades. While once a blue state, West Virginia is now safely in the hands of Republicans, which means that Gov. Jim Justice will almost certainly be the next Senator from the Mountain State. His opponent, Glenn Elliot, is former Mayor of Wheeling, West Virginia, and has been endorsed by Manchin.

Virginia

Though Virginia could be a reach for Republicans, polls have shown that the state is in play, both in the presidential and senate race. Incumbent Senator Tim Kaine (D) is an established and well-liked Virginia politician, having been the state’s Governor before being elected to the Senate in 2013. His challenger is Hung Cao, a Vietnam immigrant whose family escaped that nation’s communist regime just before the fall of Saigon. Cao served as a Special Operations Officer in the U.S. Navy, deployed on missions to Afghanistan, Iraq, and Somalia. The weekend before Election Day, Sen. Kaine made a campaign appearance on “Saturday Night Live”, evidence that this race is extremely close.