Rep. Ed Markey of Massachusetts has the backing of another progressive group in his bid for Secretary of State John Kerry's former Senate seat.

Democracy for America, the political action committee founded by former Vermont Gov.and former Democratic National Committee Chairman Howard Dean, announced its support for Markey on Monday, saying the longtime congressman is better suited for the role than his primary opponent, Democratic Rep. Stephen Lynch.

The two will go head to head next month (April 30) in the primary for the June special election.

Describing Markey as "the only tried and true progressive in the race," the group's political director, Michael Langenmayr, said in a statement that Markey has a "long record of standing up to conservative Democrats on health care and climate change."

Unlike Lynch, a social conservative from South Boston, Markey has wide support from the Democratic establishment in Massachusetts and Washington. Kerry himself backed Markey before he was confirmed as secretary of state.

According to the group, DFA has more than 33,600 members in Massachusetts. The group rallied behind Elizabeth Warren's successful campaign to unseat Sen. Scott Brown last fall.

Its members donated more than $373,000 to her campaign and 142 volunteers knocked on nearly 2,000 doors for Warren.

Last week, another liberal group, MoveOn.org, threw its support behind Markey.

Gov. Deval Patrick appointed William "Mo" Cowan, his former chief of staff, to fill the seat as an interim senator until the special election this summer.