Plummer struck a conciliatory note in his statement, thanking Harriman for his service.

"My thoughts and prayers go out to Brad and his family as he deals with his medical condition. He had a distinguished career as an educator and leader in the area, and I wish him the best," he said. "My campaign will continue to provide residents of the 12th District a new direction to shrink the size of government, reduce regulations on small businesses and best utilize the natural resources of our state."

After Harriman's announcement, Costello ruled out a bid to serve one more term.

"Brad's decision to end his campaign due to health problems is understandable, and I wish Brad the very best in the future," he said in a statement. "As you know, I announced last October that I will not seek re-election, and I am not going to reconsider and will not be a candidate for reelection."

A replacement for Harriman will be chosen by the Democratic Party chairs from each of the 12 counties in the district, who will have a weighted vote based on the number of Democratic votes cast in the March primary. Costello will co-chair the committee.