If Brown were to win the presidency, the state’s newly elected GOP governor, Mike DeWine, would get to fill his Senate seat with a Republican until the next statewide election. That means Democrats would need five total flips just to claim a bare majority capable of governing in the initial years of their new administration. And given that, once again, Brown’s main appeal is that he’s the only Democrat seemingly capable of winning in Ohio, his seat could be lost for the foreseeable future.

Brown isn’t the only candidate who needs to make this sort of tough calculation. Instead of running for president, Beto O’Rourke could try to go after Texas Sen. John Cornyn’s seat in 2020. Montana Governor Steve Bullock might be interested in the Oval Office. But he might be be more useful taking on on Republican Sen. Steve Daines. West Virginia’s Richard Ojeda, who went so far as to announce his presidential bid on Monday after losing his House bid last week, might do better to try to knock off Sen. Shelley Moore Capito. But with Brown, the tension is a bit more clear, both because he’s such a compelling presidential candidate on paper, and because winning the presidency would actually guarantee that his Senate seat flipped, rather than simply remain in Republican hands.