Key Facts
- More than one third (34 of 100 seats) of the Senate will be up for reelection in November 2024.
- The Democrats hold a two-seat edge in the Senate, and control of the Senate will likely come down to a handful of swing states.
- Republicans are favored to gain control of the Senate.
The 2024 presidential race has attracted the lion’s share of media attention in 2023 and early 2024, but control of the Senate will also be at stake on election day in November. More than one third of all Senate seats will be up for grabs.
Out of the 100 seats (two from each state), 33 incumbents will have their six-year terms expiring. A 34th seat will be decided in a special election, after Nebraska senator Ben Sasse, a Republican, stepped down to take a job as a university president. Voters will decide who fills the final two years of his term. (Another special election will determine the final two months of a California senate seat, and the next full term of that seat is also on the ballot).
Small Changes Have Big Impact
While a third of the Senate could change, it will only take a very small shift to change the balance of power in that house of Congress. Currently, the Senate is made up of 49 Republicans, 48 Democrats, and three independents. All three independents vote with the Democrats, though, giving that party a 51-49 edge in all votes.
The U.S. vice-president casts the deciding vote in any ties, so if the Republicans win the presidency, they would only need to flip one Democratic seat their way to get the majority advantage. If the Democrats win the presidency, the Republicans would need to flip two seats.
Turnover
So far, a number of senators have declared that they will not be running for reelection. Obviously, an incumbent usually has an advantage in most races, due to experience, name recognition and a better fundraising apparatus already in place. So those races where the incumbent is off the table are worth watching.
In addition to Nebraska’s Ben Sasse, only two other Republican incumbents have announced they won’t be up for reelection. Utah’s Mitt Romney is retiring, and Indiana’s Mike Braun is running for governor.
Five Democrats are retiring—West Virginia’s Joe Manchin, California interim senator Laphonza Butler, Michigan’s Debbie Stabenow, Maryland’s Ben Cardin and Delaware’s Tom Carper.
Based on early analysis, the three Republican seats appear to be safely in Republican hands again, and three of the five Democratic seats are also unlikely to flip. The two races to watch among departing incumbents are Michigan and West Virginia.
Other Battleground States
While the margin in the Senate is about as tight as it can get, that’s not the case in most races. A look at the over/under cutoffs for victory margin by state emphasizes that fact. According to one of our top politics betting sites, BetOnline (find out more with our BetOnline Review), the over/under for Republican victory margin in Florida is 19.5 percentage points. It’s 16.5 points in Mississippi, 23.5 in Nebraska, 25.5 in Utah.
On the Democratic side, the over/under for victory margin in Hawaii is 39.5 points. It’s 19.5 in Joe Biden’s home state of Delaware, 31.5 in Maryland, 26.5 in Massachusetts and 24.5 in New York.
So, with a majority of races shaping up to be blowouts in one direction or the other, the control of the Senate will likely come down to a handful of races across the country.
- Arizona: This state is considered a near tossup. The incumbent is Krysten Sinema, who aligns with the Democrats, but not closely enough for many in the party. The Democrats are running their own candidate, Ruben Gallego, against her. The Republicans currently have two candidates in the mix. BetOnline has the Democrats as -180 favorites to retain control of the seat.
- Michigan: The lack of an incumbent has this state as a possibility to flip from Democrat to Republican. A large number of candidates, including actor Hill Harper, are running. The Democrats are -300 favorites to keep the seat.
- Montana: The Republicans have this race circled as a chance to gain a seat. Incumbent Jon Tester, a Democrat, is considered vulnerable. Tim Sheehy and Matt Rosendale are vying for the Republican nomination. BetOnline has this race at -300 to flip Republican.
- Nevada: Democratic Jacky Rosen is considered vulnerable and faces a slate of Republican challengers vying for that party’s nomination. Dems are still -200 favorites to keep the seat.
- New Jersey: Incumbent Bob Menedez, a Democrat, is facing indictment, but it appears he’s still planning to run. A number of Democrats plan to challenge him for the nomination, and Republicans are also lining up. It’s still a likely Democrat lean, with the BetOnline cutoff for victory margin in double digits in favor of the Dems.
- Ohio: This might be the state that keeps us up late. It’s considered a virtual toss-up, with a number of Republicans challenging incumbent Sherrod Brown. Republicans are -120 to flip it.
- Pennsylvania: Bob Casey is the Democratic incumbent. He’ll be challenged by Dave McCormick, who ran for the Republican nomination for the other Senate seat two years ago but lost in the primary to Dr. Oz. The Dems are -275 favorites to hold serve.
- Wisconsin: No Republican has held this seat since 1952, but it will be a closer race than usual, with incumbent Tammy Baldwin facing a challenge. Odds are still -250 in favor of the Democrats.
The Pick
Add it all up, and things look good for the GOP. Remember, Republicans only need to win one or two seats to flip the Senate. West Virginia appears to be in their column, so the Republicans need to either win the presidency or one more seat in the battleground races. Nearly all the tight races have Democratic incumbents, so the Republicans likely won’t suffer any flips in the opposite direction.
BetOnline has the Republicans as -700 favorites to take control, with the Dems at +400. Bovada (find out more with our Bovada Review) doesn’t have betting on Senate control yet, but it has a generic Democrat vs. Republican senate odds. “Any Republican candidate” is a -145 favorite, to +110 for “any Democrat.”
The Pick: Republicans to Take Control (-700) at BetOnline
