A Minnesota man who posed as a police officer and knocked on lawmakers' doors in the middle of the night, killing the top Democrat in the state House and her husband and wounding a state senator and his wife, pleaded guilty to murder on Thursday so that federal prosecutors would not seek the death penalty.

The narrow upset Tuesday revealed cracks in President Donald Trump's coalition in the deep-red state, encouraging Democrats who are hopeful they can flip control of the governor's office this year.