"I met with and was inspired by a diverse cross section of individuals. I listened to business, civic and religious leaders, donors and activists, Democrats and Republicans, and of course, some regular folks who yearn for stronger communities and a thriving nation," he said.

Pesner's decision not to run further clears Rep. Edward MarkeyEdward (Ed) John MarkeyNet neutrality supporters predict tough court battle over FCC's repeal plan Avalanche of Democratic senators say Franken should resign Driverless car bill hits Senate speed bump MORE's path to the Democratic nomination. He is thus far the only candidate to announce his intentions to run if Kerry is confirmed as secretary of State, as is expected within the next few weeks.

Lynch is still mulling a run, however, and could make that decision soon, but Markey has received the backing of a number of prominent Democrats, including the Democratic Senatorial Campaign Committee, which will make him a difficult candidate for Lynch to beat in a primary.

Former Sen. Scott Brown (R-Mass.) is considered by Republicans in the state to be the most likely GOP candidate for the seat.