Imagine that Trump’s approval increases, Democrats in key races stumble, that the polls underestimate Republicans and that the underlying partisanship of some of these red states with Democratic senators reasserts itself. Basically, imagine that everything goes right for the Republicans, but that nothing extraordinarily good happens for them.

In this great-for-Republicans-but-not-unthinkable scenario (the scenario that’s better than 90 percent of the others for the GOP), Republicans get 55 seats. And, interestingly, the model doesn’t have one opinion on what a 55-seat GOP margin would look like.

In basically every case where the GOP gets 55 seats, the party defends the safe red states, Texas and Tennessee, and then takes North Dakota. That gets the GOP to 50 seats. The other five seats usually come from a combination of Nevada, Missouri, Florida, Indiana, Arizona, Montana, and West Virginia. The model thinks that Missouri and Nevada are the easiest pickups of the bunch, that Indiana and Florida are a notch tougher and that West Virginia and Montana are a bit more difficult to pick up than the others. And, interestingly, these 55 GOP seat scenarios occasionally involve Republicans grabbing an unexpected win in Wisconsin or Minnesota’s special election.