Although most competitive Senate races in 2020 involve Republicans defending their seats, it’s a Democratic senator who tops the list of the most vulnerable incumbents in the chamber one year out from Election Day.

Alabama’s Doug Jones is running for a full Senate term after winning a special election in 2017, and he faces the difficult task of overcoming the partisan dynamics of a deeply Republican state. Michigan Sen. Gary Peters is the other Democrat running in a state that President Donald Trump won in 2016, but he is further down the list, since Trump won the Wolverine State by a much smaller margin.

Democrats are largely on offense in Senate races in 2020. They need a net gain of four seats to win the majority, or three if they win the White House since the vice president would be the tie-breaking vote. Most of the other senators in vulnerable positions are Republicans, two of whom are running in states that Hillary Clinton won in 2016 — Cory Gardner of Colorado and Susan Collins of Maine. Gardner is the second-most vulnerable in the country, given that Clinton won his state by 5 points and Democrats were successful there in 2018.

Considering the high-profile backlash to Collins after her vote for Supreme Court Justice Brett M. Kavanaugh last year, it may be surprising that she is further down the list, but that’s in part because of her strong personal brand in the Pine Tree State.