First John Kerry. Then Vicki Kennedy. And then the head of the Democratic Senatorial Campaign Committee. In quick succession on a Friday afternoon, all three lined up behind Congressman Ed Markey’s bid for Kerry’s Senate seat.

“While I began last week to formally step out of politics and it's very important that I respect the apolitical nature of the post I hope to soon occupy, as Massachusetts' senior senator today and as a colleague of Ed Markey's for 28 years, I'm excited to learn of and support his decision to run for the United States Senate,” said Kerry, who is expected to become President Obama’s chief diplomat next month.

The DSCC circulated Kerry’s comments, and then emailed out a statement from its chair, Colorado Sen. Michael Bennet. “At a time when the country needs real leadership that looks out for the middle class, Ed Markey always remembers where he came from and will continue the hard work needed to turn our economy around,” Bennet said. “He is exactly the kind of leader Massachusetts needs in the US Senate.”

Vicki Kennedy, the widow of the late U.S. Sen. Edward Kennedy, issued her own statement of support for Markey, a Malden Democrat.

A special election will likely occur in summer 2013. Candidates said to be mulling a bid include Congressmen Michael Capuano (D-Somerville) and Stephen Lynch (D-South Boston), and state Sen. Ben Downing (D-Pittsfield).

Outgoing Sen. Scott Brown, a Wrentham Republican who was defeated by consumer advocate Elizabeth Warren in November, has not publicly indicated whether he will jump into the fray and attempt a return to the Senate.