Update: WCSH reports that Chellie Pingree will not enter the Senate race and will run for reelection in her House seat. Here's her statement:
After careful consideration I have decided to run for re-election to the U.S. House this year. This has been a very difficult decision and I will always be grateful for the tremendous support I've received from people all across Maine and around the country. I have been humbled by the enthusiastic encouragement I've gotten-from my neighbors here in Maine to my colleagues in Washington.
There is much at stake in this election and although the prospect of running for and possibly serving in the United States Senate was very exciting, in the end I concluded that I will best serve the people of Maine by running for re-election to the House.