Newton Mayor Setti Warren has become the second prominent Democrat to join the race to challenge Sen. Scott Brown (R).
 
Warren released an announcement video on his website Monday and plans a formal rollout Tuesday. In his early 40s and a mayor for little more than a year, Warren acknowledges that he is largely unknown to the voters of Massachusetts.
 
“Many of you don’t know me. I’m probably about as well-known as Scott Brown was at this point two years ago,” he said in the video, before walking viewers through a detailed biography.
 
Some Democrats, in Massachusetts and on Capitol Hill, are excited about Warren, an African-American who completed a tour of duty as an intelligence specialist in Iraq and previously served in the Clinton White House and as an aide to Sen. John Kerry (D-Mass.).
 
Warren joins a Democratic field that already includes City Year founder and 2009 special election candidate Alan Khazei, in addition to second-tier candidates Bob Massie — a local activist — and immigration attorney Marisa DeFranco.
 
In his announcement video, Warren addresses Brown directly.
 
“I believe Scott Brown is an honorable man. But he has not been the independent voice in the Senate that so many expected him to be,” he said, noting that the Republican Senator has voted with GOP leaders 87 percent of the time.
 
Roll Call rates this race a Tossup.

Watch Warren’s announcement video: