U.S. Rep. Stephen Lynch (D-South Boston) will run for the U.S. Senate seat vacated by former Sen. John Kerry, according to a video published by his campaign.

Lynch is expected to make a formal announcement at 4 p.m.

The ad strikes a populist note, covering Lynch's biography and reviewing some of his votes in Congress.

"He began in public housing," the ad begins. "His mother was a postal clerk. His father an ironworker. Stephen Lynch joined his father and worked 18 years as an ironworker, went to college at night, then law school, the State Senate and the United States Congress."

It continues that Lynch was "one of just two Massachusetts Representatives to vote against the $700 billion Wall Street bailout, because it did everything for Wall Street, and nothing for the people they hurt."

Lynch, who is pro-life, and voted against the Affordable Care Act distances himself from Republicans in the ad, saying Lynch was "standing firm against Republican attempts to privatize Social Security and Medicare."

The ad closes with a link to Lynch's campaign website, which as of publication, had not been launched.