youtube.com/watch?v=Nv5IqKnO39g

As expected, Rep. Stephen F. Lynch on Thursday launched a bid for Senate, releasing a YouTube video and barnstorming around the state. The official announcement is scheduled for Thursday afternoon at a hall at Ironworkers Local 7 in South Boston, Lynch’s home turf.

The Web video telegraphed some themes voters can expect to to hear from the congressman as he takes on his colleague, Rep. Edward J. Markey, in the Democratic primary for the special election being held to replace resigning Sen. John Kerry, who will be soon be sworn in as the secretary of State.

“Lynch has never forgotten where he came from,” a male narrator with a syrupy voice says of the congressman, a former ironworker. “Stephen Lynch for Senate. He’ll go to Washington to stand up, not to fit in.”

Markey has the backing of the Democratic establishment in Washington, D.C., along with the endorsement of Kerry and others.

Voters will make their choice April 30.

Former Sen. Scott P. Brown, a Republican who lost to now-Sen. Elizabeth Warren in November, has not yet said whether he’ll enter the race.