Former Massachusetts governor and 1988 Democratic presidential nominee Michael Dukakis will formally endorse Rep. Mike Capuano in the Democratic primary for the Senate special election Sunday at an event in Brookline, Mass.

Dukakis, the state’s longest-serving governor after serving from 1975-79 and again from 1983-91, joins his wife, Kitty, in endorsing Capuano in the four-person race. The primary election is Dec. 8.

In a statement issued by the Capuano campaign, Dukakis said he met the six-term Congressman “as a young staffer at the State House,— then “watched him grow and develop into one of the best mayors in the Commonwealth— and “worked closely with him since his election to Congress.—

“Mike’s passion for public service and his dedication to his constituents are obvious. But it is his courage and his conviction on the important issues of the time that impress me most of all,— Dukakis said.

Capuano is scrambling to close the gap in the polls with Democratic frontrunner Martha Coakley, the state’s attorney general, in the next 10 days. The latest surveys of the primary field have him firmly in second place, ahead of investor and Boston Celtics co-owner Stephen Pagliuca and community service leader Alan Khazei.

Khazei rolled out his own set of endorsements from more than 500 Massachusetts citizens and more than 100 national leaders on Saturday at a “statewide canvass kickoff— in Boston. Among his list of backers was Steve Case, co-founder and former CEO and chairman of AOL; New York Mayor Michael Bloomberg; Paul Fireman, the former CEO of Reebok; and J.J. Abrams, director of the television show “Lost.—

On Friday, Coakley’s campaign announced the endorsement of four past and present elected officials from Somerville, Mass., a dig at Capuano, Somerville’s mayor from 1990-99.

The winner of the Democratic primary is expected to win the general election on Jan. 19.