Adam Cote came in behind Mills with 45.93 percent.
Election staff first released the votes from the night of the primary over a week ago. But on Wednesday night the votes were tabulated.
Election officials used a computer algorithm to get a majority winner via ranked-choice voting rounds. The ranked choice rounds reallocated votes until a majority winner was found. Mills came out victorious after four rounds were conducted.
Mills, the state's Attorney General, spoke about causes she cares about in Downeast and Central Maine.
She mentioned she wants to reopen the Downeast Correctional Facility, and protect the blueberry and fishing industries.
"I want to bring good paying jobs, I want to expand broadband to areas like Washington County," said Mills. She said that "bringing infrastructure to the rim counties that don't have good infrastructure now is really key."
Mills also said she approved of the ranked choice voting process and that ranked choice deserves the trust of voters. She mentioned she wants to run a clean campaign.
The Democratic nominee for Maine's 2nd Congressional District , who will try to replace Republican Rep. Bruce Poliquin, was also announced Wednesday night. That nomination went to Jared Golden.
Detailed summary reports of the results will be posted on the Secretary of State's website.