Collins made her formal announcement in an email to supporters, saying her “bipartisan commonsense approach” has been key to many legislative successes and will be important in an era of bitter partisanship.

“The fundamental question I had to ask myself in making my decision was this: In today’s polarized political environment, is there still a role for a centrist who believes in getting things done through compromise, collegiality, and bipartisanship? I have concluded that the answer to this question is ‘yes’ and I will, therefore, seek the honor of continuing to serve as Maine’s United States senator.”

Collins’ campaign for a fifth term could be her most difficult race yet and is projected to be the most expensive political race in Maine history.