Senate math: The 13 races and four seats that decide Congress

The United States Senate holds 100 seats, and 35 of them are on the ballot today, November 3, 2026. This number includes 33 regular elections and two special elections to fill the remainder of the terms held by Marco Rubio in Florida and JD Vance in Ohio. Republicans currently hold 53 seats, while Democrats hold 45. Two independent senators caucus with the Democrats, giving the minority party a functional total of 47. The arithmetic of this chamber is precise. Democrats require a net gain of four seats to secure a majority. Republicans can lose no more than two seats to retain control. These thresholds define the strategic landscape for every campaign manager working in the 13 battleground races identified by Ballotpedia.

The geographic distribution of these seats creates distinct challenges for both parties. Thirteen of the seats are held by Democrats, and 20 are held by Republicans. However, the number of open seats significantly alters the dynamic. Eleven senators are not running for re-election, including four Democrats and seven Republicans. This retirement wave has opened seats in Iowa, Michigan, Montana, Nebraska, New Hampshire, North Carolina, and Texas. The Associated Press notes that these open seats often provide a clearer path for challengers because voters are not casting a vote on a specific incumbent's record.

The ratings for these 13 races were compiled as of October 27 by major polling aggregators, including Cook, Decision Desk, Inside Elections, and Sabato. Maine is currently a toss-up on all four major trackers. Iowa is rated either a toss-up or a lean Republican race. Kansas is viewed as a toss-up to lean Republican. Alaska and Michigan are rated as toss-ups to lean Democratic. Georgia is considered a lean to likely Democratic race. These ratings suggest that the final outcome of Senate control may hinge on the performance in just a handful of these states.

In the Northeast, the battle for control is particularly focused on Maine. Senator Susan Collins, a Republican, is facing Democratic former state Senate President Troy Jackson. Economic strain and tariffs have made the state more competitive than in recent cycles. In New Hampshire, Democratic Representative Chris Pappas is challenging former Republican Senator John E. Sununu for the seat vacated by Jeanne Shaheen. The 2024 presidential margin in New Hampshire favored Kamala Harris by 2.8 points, which has made the race tighter than historical averages would suggest.

The Midwest offers a mix of open seats and incumbent defenses. In Michigan, Gary Peters is retiring, leaving an open seat. The 2024 margin there was only 1.4 points for Donald Trump. The race features Republican former Representative Mike Rogers against Democrat Abdul El-Sayed. In a notable development, El-Sayed's former primary opponent, Haley Stevens, endorsed Rogers on Sunday. In Iowa, Joni Ernst is retiring, and the seat is considered a toss-up or lean Republican given the 13.2 point margin for Trump in 2024. Minnesota also has an open seat following the retirement of Tina Smith, with four candidates in the race, including Democratic Lieutenant Governor Peggy Flanagan and Republican Michele Tafoya.

The South presents the most complex landscape, with several open seats and high-stakes matchups. In North Carolina, Thom Tillis is retiring after clashing with President Trump. Democratic former Governor Roy Cooper is running against Michael Whatley, a former Republican National Committee chair. The 2024 margin in North Carolina was 3.3 points for Trump. In Georgia, Senator Jon Ossoff is defending his seat against Republican Representative Mike Collins. The state voted for Trump by 2.2 points in 2024, but the race is rated lean to likely Democratic. In Texas, the special election for the remainder of John Cornyn's term features Republican Attorney General Ken Paxton against Democrat James Talarico. Trump backed Paxton over Cornyn in the primary, a decision that has shaped the dynamics of the general election.

The Mountain West and Plains states are also critical to the equation. In Kansas, Roger Marshall is defending his seat in a state that has become central to the fight for Senate control. The 2024 margin was 16.2 points for Trump, yet the race is rated toss-up to lean Republican. In Nebraska, Pete Ricketts is running in a state where Trump won by 20.3 points in 2024. The seat is considered a lean Republican race. In Montana, Steve Daines is retiring, leaving an open seat in a state that voted for Trump by 19.9 points. The combination of these margins and open seats makes the region a key area for Republican defense.

In Alaska, the special election for the remainder of Marco Rubio's term is being contested by Ashley Moody, a Republican. The state voted for Trump by 13.1 points in 2024, and the race is rated toss-up to lean Democratic. The Trump administration has filed a lawsuit related to the certification of the Senate result in Alaska, adding a layer of legal complexity to the race. In Ohio, the special election for the remainder of JD Vance's term features Jon Husted, a Republican, against former Senator Sherrod Brown. The 2024 margin in Ohio was 11.2 points for Trump, and the race is a key test for Republican retention in the Midwest.

The financial aspect of the Senate race is also significant. The 2026 elections are likely to be the most expensive in history. Republican committees have outraised and outspent Democratic committees, aided by Trump-affiliated groups and Elon Musk. However, at the candidate level, Democrats have outraised their opponents. An analysis of AdImpact data shows that 88.1% of Republican general election TV ad spending went to states and districts that Trump won in 2024. This includes more than $850 million in spending in areas where he won by 10 points or more. This heavy spending in safe Republican areas contrasts with the Democratic focus on competitive states.