John Cornyn’s (R-Tex.) primary loss to Ken Paxton (R) on May 26 is the first instance of a fourth-term senator losing re-election in the 21st century. Since 2000, only five senators who served three or more terms, including Cornyn, have lost their primary bids for re-election, including Joe Lieberman (I-Conn.), who went on to win a third-party campaign. Overall, 16 senators running for a fourth term or higher have lost re-election bids since 2000.

Of the sixteen senators, nine were Democratic senators, and seven were Republicans. Eleven lost bids for a fourth term, two lost bids for a sixth term, and one each lost bids for a fifth term and a seventh term. The longest-serving senator to be defeated at this time was Richard Lugar (R-Ind.), who lost his re-nomination bid for a seventh term. The longest-serving senator to lose a general election in this time was William Roth (R-Del.), who, in his campaign for a sixth term, was defeated by Tom Carper (D-Del.) in 2000. The year with the most defeated multi-term senators was 2010 and 2024, when three senators each lost re-election.

In 2026, including Cornyn, seven Senators in their third term or higher are running for re-election. Of these members, only one, Susan Collins (R-Maine), is in a race that media outlets consider a toss-up. Prior to Cornyn’s defeat, Sabato’s Crystal Ball and The Cook Political Report with Amy Walter rated the Maine race as Likely Republican. 

Collins is the longest-serving of this cohort, along with Sen. Jack Reed (D-R.I.). Both are seeking a sixth term. If Collins wins re-election, she will become the longest-serving senator in Maine history, and if Reed wins, he will tie Clairborne Pell (D-R.I.) for Rhode Island’s record. Collins is the only Republican Senator up in a state Kamala Harris (D) won in 2024, and since the adoption of the 13th Amendment in 1913, Reed is only the fifth person to hold Rhode Island’s Class 3 Senate seat.

Of the Senators that have faced primaries thus far, most have either won with over 60% of the vote or were uncontested. Only two incumbents, Cornyn and Lindsey Graham (R-S.C.), won less than 60% of the vote. In the primary, Graham received 56% of the vote, while Cornyn received 37% of the vote in a runoff. Only Reed has yet to face a primary. Rhode Island’s primary is on September 9, and Reed and Connor Burbidge (D) are running.

To read more about Senate elections in 2026, click here.