With the midterms in the rearview mirror, all eyes are on 2024 as Republicans seek to flip both the White House and Senate.

Democrats will be defending 20 Senate seats in 2024, two of which Republicans need to flip to win the chamber. (DDHQ)

Could the Senate flip? It's likely: Democrats are defending seats in three states that voted for Trump twice. (CNN)

In contrast, Republicans are defending 11 seats in 2024, none of which are in states carried by Biden in 2020. (DDHQ)

TL;DR: the Senate majority will be up for grabs in 2024. Here are three races that could make or break Democrats' majority.

1. West Virginia will be a top target for Republicans in 2024 as they seek to unseat Democratic Sen. Joe Manchin.

Manchin is 2024's most vulnerable Democratic incumbent: former Pres. Trump won the state in 2020 by 38.9 points. (BP)

Republicans also have a strong candidate in Gov. Jim Justice, who announced his 2024 Senate run in April. (AP)

Manchin has yet to announce a reelection bid: he told NBC News in April that he would make a decision at the end of 2023.

2. Montana Sen. Jon Tester will also face a tough reelection battle in 2024 as he defends a seat in a deep-red state.

Tester is the second-most vulnerable Democrat in 2024: Montana voted for Trump by 16.4 points in 2020. (BP)

Who will face Tester? According to NBC News, GOP Rep. Matt Rosendale could jump in the 2024 race for a rematch.

Rosendale ran against Tester for the Senate in 2018 and lost by 3.5 points with 46.8% of the vote. (DDHQ)

Tester could prevail again in 2024: a Feb. The Political Company poll showed him leading Rosendale by five points.

3. Ohio Sen. Sherrod Brown is another Democrat facing reelection in a state that voted for Trump twice.

Trump carried Ohio in both 2016 and 2020 by eight points. GOP Sen. J.D. Vance also won the state in 2022 by 6.1 points.

What does the GOP primary field look like? State Sen. Matt Dolan announced a 2024 Senate run in Jan.. (ABC News)

Republican businessman Bernie Moreno also announced a 2024 Senate run in April. (CNN)

Is Brown toast? Well, not exactly: the Cook Political Report has rated the Ohio Senate race a "toss-up."