Democrats have captured Alaska ’s governor’s seat for the first time in nearly three decades, marking another major victory for their party in a midterm election period that has dramatically shifted political power across the US.

Former Alaska state legislator Jonathan Kreiss-Tomkins defeated three Republican opponents, including a candidate backed by Donald Trump , becoming the first Democrat elected governor of Alaska since 1998.

His victory – called by the Associated Press on Friday, 10 days after the polls closed – adds to a growing list of Democratic gains nationwide, bringing the party’s total to 30 US governorships.…