The Democratic primary field is already crowded, with six candidates in and former Consumer Financial Protection Bureau special adviser Elizabeth Warren doing a listening tour and seemingly gearing up to launch a bid as well. A Tolman entrance would also have splintered further the already finely diced left wing of the Massachusetts Democratic Party. His good government credentials, from his days as a "Clean Elections" candidate and legislative insurgent under a conservative Democratic speaker many critics derided as autocratic, are strong. But they find supporters among blocs of activists already committed to other clean-government Democrats in the race, like former lieutenant governor nominee Bob Massie and CityYear co-founder Alan Khazei. Tolman, an attorney at Holland & Knight and regular commentator on Boston television, has told associates he was reluctant to commit to a job in Washington that would pull him away from his family. And there's another family entanglement -- his brother Steven, a state senator, recently launched a campaign for the presidency of the state AFL-CIO.