As the closely contested election reaches its climax, the United States finds itself in a state of uncertainty. According to the latest forecast from 538, Vice President Kamala Harris and former President Donald Trump are engaged in a neck-and-neck battle for the presidency.
The balance of power in the U.S. House of Representatives hangs delicately in the balance. However, the outcome in the U.S. Senate lacks the same level of suspense.
538 is now releasing its forecast for the upper chamber. According to our analysis, Republicans have an 87% chance of winning a majority, which includes scenarios where the Senate is evenly split but President Trump’s Vice President, JD Vance, serves as the tiebreaker.
On the other hand, Democrats have a 13% chance of retaining their majority, which is roughly equivalent to rolling a die and getting a one.
Democrats face a bad map
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Our forecast takes into account the strong division that exists in America today. The Democrats are facing a challenging situation due to the unfavorable map they have to work with. Currently, the party, along with the four independents who caucus with them, holds 51 seats in the Senate.
However, one of those seats, in West Virginia, is almost certain to flip to Republicans with the retirement of Sen. Joe Manchin. This brings the Democrats down to 50 seats as a starting point.
Additionally, the party has to defend two more seats in states that traditionally lean towards the Republican party.
In Ohio, Democratic Senator Sherrod Brown is facing a close race against Republican businessman Bernie Moreno. Brown previously won this seat in 2018 by a comfortable margin of 7 percentage points.
However, it’s important to note that 2018 was a favorable year for the Democrats, and we cannot necessarily expect the same level of turnout advantage in a presidential election year. Additionally, we should not anticipate a significant amount of split-ticket voting.
According to the analysis, if we consider only the “fundamentals” such as Ohio’s partisanship and the strength of Brown as a candidate, the model predicts that he would lose by 1.1 points.
However, it is important to note that there is a significant amount of uncertainty surrounding this estimate, with the confidence interval ranging approximately from R+15 to D+14.
The polls, when combined with the underlying factors, indicate that the outcome of the Ohio election is uncertain. There is a 56-in-100 chance that Brown will emerge as the winner.
In Montana, an unlikely state for a Democratic senator, Senator Jon Tester stands out. He is not your typical Democrat. Tester, who refers to himself as a “dirt farmer,” has a diverse background working as a teacher, butcher, and state senator before entering federal politics.
Despite the state’s conservative lean and the increasing margin by which it has voted for Republican presidential candidates (from 2 points in 2008 to 16 points in 2020), Tester’s rural charm and local connections have enabled him to defy these odds and secure his position in office.
The rest of the field
In Nevada, Democratic Senator Jacky Rosen is highly likely to defeat Republican veteran Sam Brown, with a 91-in-100 chance.
Meanwhile, in Arizona, Democratic Representative Ruben Gallego has an 88-in-100 chance of securing victory over Republican former TV news anchor Kari Lake to fill the seat being vacated by independent Senator Kyrsten Sinema.
In the northern battlegrounds, there is a higher likelihood of a Republican upset. Democratic Rep. Elissa Slotkin in Michigan has a 77-in-100 chance of defeating Republican former Rep. Mike Rogers and succeeding retiring Democratic Sen. Debbie Stabenow.
Similarly, Democratic Sen. Tammy Baldwin in Wisconsin has a 78-in-100 chance of beating Republican investor Eric Hovde. In Pennsylvania, Democratic Sen. Bob Casey Jr. has a very similar 79-in-100 chance of winning over Republican hedge fund manager Dave McCormick.
While Democrats maintain their lead in all three of these seats, there is still a possibility for Republicans to emerge victorious in at least one of these races, should there be a normal-sized polling error.
This provides Republicans with an alternative route to securing control of the Senate, even if Democrats are able to retain their seats in Montana and Ohio.
In contrast, Democrats face limited opportunities to flip Republican-held seats and are often considered underdogs in those races. For instance, in Florida, Republican Sen. Rick Scott is highly favored with an 83-in-100 chance of winning reelection against his Democratic opponent, former Rep. Debbie Mucarsel-Powell. Similarly, in Texas, Republican Sen. Ted Cruz is projected to have an 82-in-100 chance of defeating Democratic Rep. Colin Allred.
Despite these challenging odds, Democrats still have a slightly better chance of picking off one of these seats than they do of holding onto Montana.
Considering that Democrats likely need to win at least one of these seats to maintain their Senate majority, it may be strategic for them to go all-in and launch an aggressive campaign against either Scott or Cruz. After all, sometimes, the best way to defend is by going on the offensive!
The regularly scheduled Senate race in Nebraska presents an interesting twist. While the Cornhusker State traditionally leans towards the Republican party, independent candidate Dan Osborn has posed a challenge for Senator Deb Fischer.
In fact, our polling average shows that Fischer is currently leading Osborn by a mere 0.9 points. Despite this close race, our forecast still gives Fischer a 95-in-100 chance of winning reelection, largely due to the strong Republican-leaning fundamentals in the state.
If Osborn were to win, it would create complications in determining the Senate majority. It is unclear whether his victory would result in a Republican hold or a Democratic gain.
Although he is running as the de facto Democratic candidate, Osborn has made it clear that he will not caucus with either party. Moreover, his conservative views make it plausible for him to align with Republicans, especially if they offer enticing incentives such as influential committee assignments.
To account for this uncertainty, our forecast randomly assigns which party Osborn would caucus with if he wins. We estimate that one-third of the time he would be counted as a Democratic senator, one-third as a Republican, and one-third as a pure independent who does not align with either party.
This election will decide Democrats’ long-term fate in the Senate
From the onset of the campaign, it was evident that Democrats faced a significant disadvantage in the 2024 Senate elections due to the unfavorable map.
However, this disparity extends beyond 2024. The overall structure of the Senate inherently favors Republicans. This is because each state is awarded an equal number of seats, and with rural areas tending to vote Republican, there are more red-leaning states compared to blue-leaning ones.
Over time, this bias has only grown, particularly as split-ticket voting has become less common. An analysis by 538 reveals that the median Senate seat after the 2020 election leaned 5 points more towards the Republican side than the nation as a whole.
Consequently, in order to secure control of the chamber, Democrats must not only win every blue state but also gain support in a few light-red states.
The 2024 map poses challenges for Democrats, but they may also face difficulties in the 2026 elections. In this upcoming election cycle, Democrats will need to defend four seats in states where President Joe Biden won by a margin of less than 8 points in the 2020 election.
These states include Georgia, Michigan, Minnesota, and New Hampshire. On the other hand, Republicans will be defending three seats in states where former President Trump either lost or won by less than 8 points, such as Maine, North Carolina, and Texas.
In 2028, Democrats will face the challenge of defending five seats that Biden won by a margin of less than 8 points. These seats include Arizona, Georgia, Nevada, New Hampshire, and Pennsylvania.
On the other hand, Republicans will only have to defend three seats that Trump either lost or won by fewer than 8 points. These seats are Florida, North Carolina, and Wisconsin.
Without a major shift in party alliances or a resurgence of split-ticket voting and localized races, the Democrats may not see another Senate majority for quite some time. Conversely, the Republicans are optimistic about the prospects of gaining seats in the Senate over the next decade.
Footnotes
Nebraska is currently holding a special election for its other Senate seat, which became vacant after former Republican Senator Ben Sasse resigned last year. However, this election is not expected to be competitive.