(CNN) - Another Massachusetts Democrat is bowing out of the race to fill Ted Kennedy's Senate seat.
Rep. John Tierney released a statement Monday saying he can "best be of service in the U.S. House of Representatives."
"Since the passing of Senator Kennedy, a great number of people have kindly urged me to run for the United States Senate," Tierney said. "Such an opportunity comes open perhaps only once in one's lifetime. I have given the matter serious consideration, and while thankful for all of the confidence shown, today I am stating that, at this time, I shall not be a candidate in the special election for the U.S. Senate."
Tierney's decision not to run leaves three Democrats likely to seek Kennedy's seat: Massachusetts Attorney General Martha Coakley officially declared her candidacy last week, while Reps. Stephen Lynch and Michael Capuano have picked up papers to run for the seat.
Other Democrats who were thought to be considering a bid but have bowed out include Rep. Edward Markey and former Reps. Joseph P. Kennedy II and Marty Meehan.
Over the weekend, Republican State Sen. Scott Brown officially jumped in the race and is considered the frontrunner for the GOP nomination.
The Democratic primary will take place on December 8, followed by a sprint to the general election, which is slated for January 19.