Rep. Michael Capuano (D-Mass.) has decided not to run for in the special election to replace Sen. John Kerry (D-Mass.), his office confirmed Tuesday.

Capuano's decision makes him the latest Democrat to opt not to run against Rep. Ed Markey in the Democratic primary.

Markey, the dean of the state's congressional delegation, has already garnered the support of Kerry, the late Sen. Ted Kennedy's widow Vicki Kennedy and the national Democratic Party -- moves that are all designed to avoid a tough primary that could give Sen. Scott Brown (R-Mass.) an upper hand in the general election.

So far, it seems to be working, as Markey has no big-name primary opposition and a number of well-known candidates have turned the race down, including Attorney General Martha Coakley, Ted Kennedy Jr., Rep. Niki Tsongas, state Sen. Ben Downing and actor Ben Affleck.

Brown has not officially announced his intentions, but he is considered the GOP's clear No. 1 option.

Capuano ran in the Democratic primary in the last special election following Kennedy's death in 2009, but he finished a distant second to Coakley, 47 percent to 28 percent.