Not much has changed over at our midterm Senate forecast. Our model has been consistently showing Democrats at a disadvantage to take back control of the chamber. According to our Classic model, the odds are 1 in 7.

We have seen a trend develop: not all the so-called “red-state Democrats” (incumbents from states that President Trump won in 2016) are faring the same. Some, like the incumbents in Michigan, Pennsylvania, Ohio and Wisconsin are doing quite well. But we have our eye on red-state Democrats in states that lean heavily Republican. We’re mostly thinking of Sen. Joe Manchin of West Virginia, Sen. Jon Tester of Montana, Sen. Joe Donnelly of Indiana, Sen. Heidi Heitkamp of North Dakota and Sen. Claire McCaskill of Missouri. Some of these senators are doing better than others.

Manchin has a comfortable 7-in-8 chance of keeping his seat, as does Tester. Donnelly has a slightly less robust lead, but our forecast still shows him with a 7-in-10 chance of winning. The red-state Democrats that look most endangered are McCaskill, who has a 3-in-5 chance, and Heitkamp who only has a 1-in-4 chance of keeping her seat.

If there is one theme that ties all these red-state Democrats’ reelection campaigns together it is “independence.” Each senator is trying to make a pitch that’s local, something along the lines of, “I’m here to protect the interests of the people of our state, not the interest of a party, and I’ll work across the aisle to get that done if need be.” They’re trying to appeal to Democrats, independents as well as a whole bunch of people who voted for Trump. That’s why you saw Donnelly make an ad that talked about the “radical left” and quoted Ronald Reagan, why Manchin reprised his shooting-a-piece-of-legislation-with-a-gun gambit (proof of independence and Second Amendment support), and why McCaskill has one spot that says she’s not “one of those crazy Democrats.”

But why are some of these red-state Democrats doing better than others? Some of these red states are redder than others. According to our partisan lean metric, North Dakota is the reddest of this group — it’s 33.2 points more Republican than the country overall, meaning Heitkamp is operating in a political environment that’s hostile to Democrats. But West Virginia is also pretty darn red — 30.5 points more Republican than the rest of the country, and Manchin is doing well there. Montana is 17.7 points more Republican, Indiana is 17.9 points more Republican and Missouri 19.0 points more Republican, yet in those three states with relatively similar levels of partisanship, it’s McCaskill that’s doing the worst.

Could something else explain Heitkamp and McCaskill’s troubles, something the forecast model can’t measure? Gender perhaps? Earlier this year, political scientist David Hopkins told my colleague Perry Bacon Jr., “There is some scholarly evidence that voters tend to perceive female politicians as more liberal than men.” Could this, coupled with recent high-profile political happenings be making an already hostile partisan environment even more hostile for these two women?

Events of the past few weeks put red-state Democrats in the uncomfortable position of deciding whether or not to confirm Supreme Court Justice Brett Kavanaugh after he was accused of sexual assault. For many of the women of the Senate, the vote went beyond a party line position and verged into the realm of the personal. Republican Sen. Lisa Murkowski voted against Kavanaugh and said when asked in an interview that she’d had her own #MeToo moment (she declined to specify further). Heitkamp voted against the nominee as well, a move that many think might have sealed her fate. The senator said the vote wasn’t political. “History will judge you but most importantly you’ll judge yourself. And that’s really what I’m saying. I can’t get up in the morning and look at the life experience that I’ve had and say yes to Judge Kavanaugh.” McCaskill voted against the judge as well.

The highly partisan nature of the confirmation vote only a few weeks before Election Day was bad news for red-state Democrats overall, reminding Republican voters in their states of the national partisan stakes of their votes. Which of these candidates win on Election Day and which lose will come down in part to the kinds of campaigns they’ve run and the natural partisanship of their state environments, of course. But politics reflects the complications of human nature. It might well be the case that, as in so many parts of life, gender biases have been rearing up.