In a huge boost to the campaign of Democrat Dannel Malloy, all six affiliates of the Service Employees International Union have endorsed his candidacy for governor.

The SEIU Connecticut State Council, which has 55,000 members, announced Monday that it will support Malloy in the Aug. 10 primary against Greenwich cable TV executive Ned Lamont.

Union endorsements are important in Democratic primaries, and the two sides have been battling for support. Unions spread the word among their members through literature both in the workplace and in direct mailings to union households in the crucial get-out-the-vote drives in the final weeks. The unions also operate phone banks to make sure their members get to the polls.

Previously, four of the six major SEIU unions had announced their support, but SEIU state council director Paul Filson said the leadership wanted to "go all in" for the Democratic ticket.

At the same time, Lamont has lined up his own support from powerful unions, including the Connecticut Education Association, the state's largest teachers' union with more than 40,000 members. He has also been endorsed by the 10,000-member United Food and Commercial Workers union, the United Auto Workers, the sheet metal workers, and the ironworkers, among others.

Like Malloy, Lamont had sought the endorsement by filling out a 19-question form and meeting with the executive council.

"SEIU — those are great folks,'' Lamont said Monday. "I respect what they do and the power they have for fighting for the middle class. If [the workers] weren't organized, they wouldn't have enough to get by. They'd be getting $10 an hour.''

Regarding the endorsement, Lamont said: "They tell me, 'Dan crosses every t and dots every i and tells us everything we want to hear.' There's no question about it. I can't out-promise Dan Malloy. I can't meet every promise down the line. ... I make promises I can keep.''

"If that's not sour grapes …,'' Malloy responded without completing the sentence. "I would love to debate him on a stage in front of TV about that. … Sometimes you have to be gracious.''

Both Malloy and his chief strategist, Roy Occhiogrosso, said the SEIU endorsement is crucial in the closing weeks. Malloy said he believes that his willingness to debate helped secure the endorsement, and Lamont's unwillingness to debate on television in New London has "backfired'' on him.

"I certainly wanted to have their endorsement — and wanted to have it four years ago and didn't,'' Malloy said.

The previous SEIU endorsements for Malloy were by District 1199, which is known as one of the state's most politically active unions, and SEIU Local 32BJ, which represents janitors and security guards. Last week, both CSEA/SEIU Local 2001 and CEUI/SEIU Local 511 stepped forward in favor of Malloy.

The coalition says the endorsements were made partly because of Malloy's record during 14 years as mayor of Stamford, from 1995 through 2009.

The shifting sands of union support represent a change from the 2006 Democratic primary between Malloy and the eventual winner, New Haven Mayor John DeStefano.

DeStefano had broad union backing, and Malloy has been working hard to gain similar support this year. In addition to being endorsed by the state AFL-CIO, DeStefano had 45 local unions behind him that made many insiders believe that he would defeat Malloy by 5 to 10 percentage points. When DeStefano won by only 1.5 percentage points, Republicans and even some Democrats questioned how much political clout the unions actually have.

DeStefano, however, did not have the support in the primary from the Connecticut Education Association, which has endorsed Lamont. The CEA did not endorse DeStefano until the morning after his victory. In addition, the food workers only endorsed DeStefano in the final week – and decided to make a much earlier endorsement this year of Lamont.

Malloy lost by less than 4,300 votes in 2006, and union spokesman Matt O'Connor says now that CSEA/SEIU Local 2001 "could be the difference in a close election.''

The local has nearly 25,000 members, including nearly 13,000 retirees, and about 8,000 of them are registered Democrats, O'Connor said.