Nearly two dozen Democratic seats are up for reelection in 2024, with five incumbents seen as vulnerable, while only 10 Republicans face reelection. However, Republicans in six critical races are trailing Trump and their Democratic opponents.  

The only Senate GOP candidate who is consistently leading is Montana Republican Tim Sheehy. In an average of polling, Sheehy is ahead of incumbent Sen. Jon Tester (D-MT) by 5.2 percentage points. However, Sheehy’s lead is not as strong as Trump’s in Big Sky Country, in which he leads by an average of 17.6 percentage points.

Senate Majority Leader Chuck Schumer (D-NY) has a 51-seat advantage and the ability to tap Vice President Kamala Harris for any tiebreaking votes. He is already expected to lose one seat in West Virginia with the retirement of Sen. Joe Manchin (I-WV). If Republicans win in Montana, they’ll be able to capture the majority, but the race for control of the upper chamber is still up in the air in a cycle that favors Republicans.

In Republican-leaning Ohio, where Trump has a 9-percentage point lead over Vice President Kamala Harris, Sen. Sherrod Brown (D-OH) is leading Republican Bernie Moreno by an average of 3.6 percentage points. 

In battleground state Nevada, Republican Sam Brown is trailing Sen. Jacky Rosen (D-NV) by an average of 10.7 percentage points, while the race for president is still neck and neck, with Trump down less than 2 percentage points in polling averages. 

In states with open seats like Arizona and Michigan, Republican candidates are trailing their Democratic opponents and underperforming Trump. GOP Senate hopeful Kari Lake is down an average of 4.5 percentage points to her Democratic opponent, Rep. Ruben Gallego (D-AZ), in the Grand Canyon State, as they face off to take over Sen. Kyrsten Sinema’s (I-AZ) seat. Lake is significantly underperforming in comparison to Trump, who is up 1.3 percentage points over Harris in the state in an average of polling numbers.

Former Republican Rep. Mike Rogers is behind opponent Rep. Elissa Slotkin (D-MI) by an average of 5 percentage points. Meanwhile, Trump and Harris are polling neck and neck with averages showing they are tied or separated by less than 1 percentage point. 

In the Keystone State, Republican Dave McCormick is down an average of 3 percentage points to incumbent Sen. Bob Casey (D-PA). Meanwhile, Trump and Harris have been tied or within percentage points of each other in the critical swing state.

Republican candidate Eric Hovde is behind incumbent Sen. Tammy Baldwin (D-WI) by an average of 5.2 percentage points. In comparison, Trump is trailing Harris in the critical Midwestern state by an average of 1.2 percentage points.

In Maryland, former Republican Gov. Larry Hogan appears to be significantly overperforming Trump in his state. A recent average of polling in the state found Hogan leading by 3.8 percentage points, while Trump is down an average of 26.5 percentage points in the state.  

Sen. Ted Cruz (R-TX), who is defending his seat this cycle, is polling an average of 6 percentage points ahead of his Democratic challenger, Rep. Colin Allred (D-TX). Trump is slightly overperforming with a 7.3-percentage point lead over Harris in the Lone Star State. 

In Florida, Sen. Rick Scott (R-FL) is polling an average of 4.3 percentage points ahead of his Democratic opponent, former Rep. Debbie Mucarsel-Powell. While the Florida senator is still ahead, he is not performing as well as the Republican presidential nominee, who is up an average of 6 percentage points over Harris in the Sunshine State.