Kyle Kondik and J. Miles Coleman explain why “Maine Moves from Leans Republican to Toss-up” in Sabato’s Crystal Ball ratings: “Gov. Janet Mills (D-ME) entered the Maine Senate race on Tuesday morning, giving Sen. Susan Collins (R-ME) a more proven potential challenger even as other Democrats are seeking the nomination…We are moving the Maine Senate race from Leans Republican to Toss-up, which means we now have four Senate Toss-ups: Republican-held Maine and North Carolina and Democratic-held Georgia and Michigan…Collins does still retain some advantages, and she may be stronger than her middling-to-poor favorability/approval numbers may indicate…Democrats do also have some potential primary headaches to navigate, which we will be exploring in further detail in the next issue of the Crystal Ball.

Earlier today, Maine Gov. Janet Mills (D) moved ahead with her long-anticipated entry into her state’s Senate contest. With that, national Democrats were at least able to recruit their preferred candidates in the two states that represent Democrats’ clearest-cut offensive opportunities on the 2026 Senate map: Maine and North Carolina. In the latter, former Gov. Roy Cooper (D) announced his campaign over the summer; we suspect he’ll be locked in a close race with former Republican National Committee Chairman Michael Whatley, who is a heavy favorite for the GOP nod, right up until Election Day 2026. And now Mills is running in Maine, although she may still face a competitive primary (more on that below).

For Democrats’ “Senate math,” it is hard to overstate Maine’s importance. Sen. Susan Collins (R) is the only Republican in the chamber who represents a state that voted against Donald Trump in all three of his general election campaigns.

We have been thinking about moving Maine from Leans Republican to Toss-up for months, and Mills’s entry is enough for us to move ahead with that change. Our main reasons for moving the race are as follows:

1. As a Republican senator in a state that votes Democratic for president, Collins is a major outlier; indeed, while Democrats do hold a number of Senate seats in states that voted for Donald Trump, they have lost all of their senators in states that are more reliably Republican for president: Their losses in Montana, Ohio, and West Virginia last year represented the “end of the line” for red-state Senate Democrats. So Collins is really the only senator among the 100 who represents a state that not only reliably votes for the other party for president, but is not really even a true presidential battleground. Trump did get an electoral vote from Maine’s 2nd Congressional District in all three of his elections, but the 1st District is bluer than the 2nd is red, which explains the state’s overall blue lean.

2. Polls differ on Collins’s approval/favorability rating, but the bulk of them point to her numbers being underwater. There was a Pan Atlantic Research poll from May that showed Collins’s favorability as 49% favorable/45% unfavorable. A University of New Hampshire poll from April, by contrast, showed her favorability split as just 12% favorable/58% unfavorable, although another 27% selected “neutral.” Back in July, Morning Consult’s quarterly approval tracking of all senators showed her approval split at 38% approve/54% disapprove. A more recent poll from a Democratic pollster, Zenith Research (run by Adam Carlson, who we sometimes cite), showed Collins at a 40%/47% favorability split. Our bottom line here is one could “choose your own adventure” and tell different stories about Collins using these different polls, but the bulk of the public data point to an underwater approval/favorability.

3. The biggest question about this race was whether Collins would face a strong Democratic opponent or not. Mills, a two-term governor, does give Democrats a credentialed recruit. Previously, the Democratic field had a number of options but lacked someone who is electorally proven: Graham Platner (D), an oyster farmer, veteran, and first-time candidate, has generated a lot of attention since announcing his candidacy a couple of months ago; Jordan Wood, a former congressional staffer, has also gotten some buzz (though not nearly to the level of Platner). Another candidate, brewery owner Dan Kleban, dropped out Tuesday and endorsed Mills. As a sitting governor and proven candidate, Mills has to start the primary as a favorite. However, if Mills were to lose the nomination to Platner or one of the others, perhaps that person will have proven themselves to be a strong candidate over the course of that race. There is also the possibility that Collins, who has not officially announced her bid for another term but has been acting like a candidate, could decide to retire.

To sum it up, we view the race as a Toss-up now because Collins is an electoral outlier; Collins’s approval/favorability numbers are not great; and the chances of the Democrats producing a strong challenger have gone up now that Mills has entered. The first two reasons have been present for months; the third one is what has changed, which tips us over into making this change now.

Still, Republicans have counterpoints to the three reasons cited above. Let’s go through those:

1. It may be that despite the decline of ticket-splitting and Collins’s position as an outlier among the senators, Maine is just a different place with more of an appetite for ticket-splitting than other states. Maine does also feature Rep. Jared Golden (D, ME-2), the Democrat who represents the reddest House district at the presidential level (Trump won it by 9 points). Maine is politically quirky and may continue to behave in ways that other states don’t, and Collins does sometimes show independence from the national Republican brand: This year, she voted against the confirmation of Pete Hegseth as Secretary of Defense and Kash Patel as FBI director and against final passage of the “One Big Beautiful Bill.”

2. That Collins sometimes votes against her own party—even as Democrats cite other votes with national Republicans, such as backing other Trump Cabinet picks and voting yes on a procedural vote for the OBBB package—might help explain why her favorability with Republicans is sometimes quite low, which drags down her overall numbers. In that UNH poll that had Collins’s favorability extremely low, only 19% of Republicans expressed a favorable view of her. Yet we would also expect these Republicans to ultimately provide her a strong level of party unity when it comes down to the actual vote in November 2026. In other words, a low favorability/approval for Collins may not be predictive because her numbers are driven down to some extent by Republicans who have no intention of voting Democratic. In a way, this may be comparable to the broader national Democratic Party favorability problems—just because the national Democratic brand is bad doesn’t mean they are doomed overall next year, because people can have a negative view of their own party (or candidate) but still vote for them because they prefer them to the alternative. Collins may have a level of strength that polling is missing—certainly the polls that showed her losing in 2020 ended up significantly underestimating her.

3. The chances of the Democrats producing a strong challenger to Collins are now higher, but it may be that the eventual Democratic nominee does not end up being that strong. For instance, what if Platner or another Democrat beats Mills in the primary but runs hard to the left in the process, taking positions that hurt them in the general election? What if Mills does the same in order to win the nomination, or what if Mills waltzes to the nomination but doesn’t end up performing well for one reason or another? Mills would be the oldest first-term senator in history if elected; as part of her announcement rollout, she said she only planned to serve a single term. We’ll look more at the primary in the next issue of the Crystal Ball, which will function as a part two of this piece.

Overall, there are reasonable rejoinders to our reasoning for making Maine’s Senate race a Toss-up. But we do think there is enough question about this race to make it a Toss-up, even as this is still a somewhat vexing race to assess: Eli McKown-Dawson of Nate Silver’s Silver Bulletin had an excellent assessment of the contradictory indicators in the race last month.

Map 1 shows our updated Crystal Ball Senate rating map. As noted above, there are now four Toss-ups. If Democrats sweep all of them and hold all of their other current seats, they would be at 49 Senate seats—still two short of a majority. So in order to compete for the Senate majority they would need to cut deeper into redder turf—this is why Republicans remain clearly favored to hold the Senate majority overall.”