New Hampshire Democratic Sen. Jeanne Shaheen’s decision to not seek reelection marks the latest bit of tough luck for Senate Democrats, who face an increasingly challenging midterm election map as they fight to climb out of the minority.

New Hampshire Sen. Jeanne Shaheen’s departure will add another Senate seat for Democrats to defend without an incumbent after Sens. Gary Peters of Michigan and Tina Smith of Minnesota

Senate Democrats are facing a flurry of retirements in key states next year, turning up the heat on already competitive races against the backdrop of an unforgiving election map heavily favoring Republicans to retain control.