The Last Crossover Senator: What the Numbers Say About Susan Collins

A category of one

Start with a single fact, because the rest of the story hangs from it. After the 2024 election, Susan Collins of Maine is the only Republican in the United States Senate who represents a state carried by the other party's presidential nominee. Kamala Harris won Maine. Collins holds the seat. She is the lone outlier in her conference, a category of one (Sabato's Crystal Ball, 2026).

That is not a talking point. It is a measurement, and it sits inside a larger count that has been shrinking for a generation. Ten senators now sit in a state their party's presidential candidate lost in 2024, the group political scientists call crossover senators. Nine are Democrats holding ground in states Donald Trump won. One is Collins (Sabato's Crystal Ball, 2026). When Maine Democrats meet in a July 27 convention to choose a replacement for Graham Platner, who suspended his campaign on July 8 after a rape allegation he denies, they are not just picking a nominee (CNN, July 8, 2026). They are trying to solve a problem that has defeated their party in Maine five times.

The spine of the number

The crossover senator used to be ordinary. Follow the count back and the decline is steep and steady. Immediately after the 2004 election there were 24 crossover senators, roughly a quarter of the chamber. After 2012 there were 21. After 2024 there are 10 (Sabato's Crystal Ball, 2026). The Senate that once held two dozen members representing hostile presidential turf now holds ten, and the number keeps falling toward the floor.

Split state delegations tell the same story from another angle. For most of the twentieth century, states routinely sent one Republican and one Democrat to Washington. After 2024, only three states do: Maine, Pennsylvania, and Wisconsin. That is the fewest split delegations since the direct popular election of senators began in 1914 (Pew Research Center, November 2024). The Pew analysts put a second number on the trend that is worth sitting with. Since 2012, 91 percent of Senate contests, 222 of 245, have been won by the candidate from the party that carried that state at the most recent presidential race (Pew Research Center, November 2024). Ticket splitting did not disappear. It became the exception that proves a hardening rule.

How one senator beat the trend

Against that current, Collins has not just survived. She has widened her margins when the models said she should shrink. Elected in 1996 to succeed William Cohen, she has won five terms. The one that matters to this argument is 2020, because it is the cleanest test the data offers.

Not a single public poll in the 2020 Maine Senate race showed Collins leading. Some showed her trailing Democrat Sara Gideon by double digits (Brookings, 2021). Money poured in against her in one of the most expensive Senate races of the cycle. When the ballots were counted, Collins won 50.98 percent to 42.39 percent, a margin close to nine points, and became the first Republican woman elected to a fifth Senate term (Maine Public, November 4, 2020). The gap between what the polls said and what Maine did was the widest of any Senate race that year. It is the reason professional handicappers still refuse to move Maine out of the tossup column even when a Democrat leads a survey.

What the record actually shows

The temptation is to call Collins lucky. The record argues something more specific and more measurable: she has built a voting and legislating profile that does not sort cleanly into either party's column, and Maine voters can see it. The Lugar Center, which scores every member of Congress on how often their bills draw cosponsors from the other party and how often they cross the aisle themselves, has named Collins the most bipartisan senator in nine of the past eleven years, the longest such run in the index's history (Lugar Center-McCourt School, 2024).

GovTrack's independent measure points the same direction. In the full 118th Congress, 66.7 percent of Collins's cosponsorships went to bills led by Democrats, the highest cross-party share in the Senate (GovTrack, 2024 Report Cards). Set that next to her colleagues and the distance is stark. Texas Republican John Cornyn crossed over on 39.1 percent of his cosponsorships; his home-state colleague Ted Cruz did so on 18.3 percent; Missouri's Eric Schmitt, the lowest in the chamber, on 13.8 percent (GovTrack, 2024 Report Cards). In our ranking of the Senate by cross-party legislating, Collins sits first. A crossover state produced a crossover record, and the record is documented, not asserted.

Why the Democrats keep trying anyway

None of this makes Collins safe, and the honest read of 2026 says so plainly. Maine is a state Harris carried. Collins would be seeking a sixth term at a moment when the president's party historically loses ground in midterms. The seat is rated a tossup by all three major raters, and it sits second on the US Political Rank board of the most flippable Senate seats, behind only North Carolina (US Political Rank, 2026). The first poll of the post-Platner field, conducted by Z to A Research on July 9, found former Maine CDC director Nirav Shah at 47 to Collins's 46, Secretary of State Shenna Bellows tied at 47, and former state Senate President Troy Jackson at 47 to Collins's 48, every pairing inside the margin of error (NOTUS, July 9, 2026).

Those numbers are real, and they concede the point that this is a genuine race. What the numbers cannot resolve is the gap between a summer poll and a Collins result, because that gap has run in one direction for a quarter century. The Democrats meeting in convention on July 27 are betting that the trend that erased the crossover senator will finally reach the last one standing. The receipts say it is possible. The same receipts say Maine has made that bet before and lost it five times.

What to watch

The tell will not be the horse-race number. It will be whether the eventual nominee can pull any of Collins's crossover coalition away from her, the Maine voters who back a Democrat for president and Collins for Senate in the same booth. That is the coalition the raw polling cannot see and the one that decided 2020. Watch the convention on July 27 for the nominee, watch the fall for whether Collins's own numbers move once she has a named opponent, and watch, above all, whether the last crossover senator holds a seat that history says should already have flipped. The evidence settles that the breed is nearly extinct. It has not yet settled that the final member of it can be beaten.