Democratic Congressman Stephen Lynch is preparing to make a major announcement.
Lynch's campaign would not confirm Tuesday what the Thursday announcement is, but Lynch is widely expected to say he is a candidate for the Senate seat being vacated by John Kerry.
Lynch will begin Thursday with stops in Springfield and Worcester with an evening event at Iron Workers Local 7 in South Boston.
The Boston Democrat has been privately telling supporters of his plans to run, although he publicly said last week that he had not made a final decision.
Fellow Democratic U.S. Rep. Edward Markey has already announced he will seek Kerry's seat.
Former U.S. Sen. Scott Brown is considering a campaign on the Republican side.
The special election will be held on June 25. The primary is set for April 30.
