“When is he going to endorse?” Lou Mandarini, the president of the Greater Boston Labor Council, said it in a high-pitched voice while looking out into a crowd of union members who had gathered at the IBEW Local 103’s headquarters in Dorchester for a rally and some red meat.

Mayor Thomas Menino sat next to him, ready to take the podium and reiterate his support for Elizabeth Warren, whom he had endorsed at a Roslindale Square rally on Friday.

“When is he going to endorse?” Mandarini said it again, in the same tone, as if to mock activists’ fretting and reporters’ questions over the last few months. Okay, so he waited for the last day of summer to do it, Mandarini continued: “He did it his way.”

For Democratic activists, the road to Roslindale had its bumps: Menino had once declared US Sen. Scott Brown “unbeatable,” and, in one mischievous television interview, he had noted that ballots are cast in secret. His absence was noted at a Boston University rally earlier this month that featured Warren and several fellow Democrats, including Gov. Deval Patrick and Congressman Michael Capuano.

But Menino did appear to lay some groundwork for the eventual endorsement at the Labor Day breakfast, deploying the phrase “Brown is a Nice Guy But,” which has become a staple of Democratic speeches.

“What’s he stand for? Mitch McConnell,” Menino asked at the union hall on Monday, referring to the Kentucky Republican who leads the minority caucus in the Senate. “That’s who he stands for.”

Warren is “good people,” the mayor said. “She’ll have our back in Washington. I’m going to have her back over the next 39 days.”

US Sen. John Kerry, who serves on Capitol Hill with Brown, endorsed Warren in Somerville on Monday morning, then joined Menino and Warren at the IBEW table.

The rally was an indication of how hard top union officials are gunning for Brown and attempting to drive their members to vote a straight Democratic Party ticket. Most unions endorsed Warren months ago, but for union leaders, keeping energy up is key, particularly since union members were split between Brown and his opponent in the 2010 special election, Martha Coakley.

For Menino, the election offers a chance to hitch an electoral ride with Warren and add a notch in his machine’s “win” column. It’s good timing for Menino, whose political team’s track record has been spotty at best in recent races where the mayor’s name isn’t on the ballot.

Boston will go big for Warren, thanks to President Obama’s long coattails at the top of the ticket. But Menino will be able to help run up the score even as Brown is likely to pick up pockets of support in areas like South Boston and Dorchester’s Neponset section.

Brown has spent plenty of time in those parts of the city, along with Adams Corner. On Saturday, he swung by the Eire Pub, after a quick lunch at Sullivan’s on Castle Island with former Mayor Ray Flynn.

Dorchester emerged as Ground Zero for the latest campaign misstep in a race plagued by silliness on both sides: The state Democratic Party promoted a video showing Brown supporters and staffers making like Native American mascots with war whoops and tomahawk chops.

Brown told reporters on Tuesday he hadn’t seen the video. “If you’re saying that, that’s not something I condone,” Brown said, according to the State House News Service. “It’s certainly something if I’m aware of it, I’ll tell that member to never do it again.” Seven police officers were outside the Eire Pub, Brown added, due to the “behavior and mob scene with a lot of her supporters.”

But Brown quickly pivoted to questions his campaign has been raising about Warren’s Native American heritage and whether she used it to advance her career, a charge her campaign has vigorously denied.

“I think the apologies that need to be made and the offensiveness here is the fact that Professor Warren took advantage of a claim to be somebody, a Native American, using that for an advantage, a tactical advantage,” Brown said.

Former Menino administration hands putting fundraiser together for October

Old hands who once worked in the Menino administration are organizing a fundraiser that will be held at the Boston Harbor Hotel on Oct. 11, more than a year before the 2013 municipal election.

“Please join Mayor Thomas M. Menino and his team as we celebrate our success, past and present, and look forward together to our city’s bright future,” says the invitation, which includes a picture of part of the Boston skyline and a building under construction.

According to the invitation, co-chairs of the fundraiser include Carole Brennan, a former Menino press secretary now at Brown Rudnick; Larry Mayes, former human services chief; Julie Burns, former arts and tourism director; Eliza Greenberg, former elderly affairs chief; and former school committee chair Elizabeth Reilinger, among others.

The prevailing view inside and outside of City Hall is that Menino will run for another term next year. His fundraising has continued apace, and he still maintains a campaign office, according to campaign finance reports.

Suggested donations for the October fundraiser include $100, $250, and $500.

EDITOR’S NOTE: Check out updates to Boston’s political scene at The Lit Drop, located at dotnews.com/litdrop. Material from State House News Service was used in this report. Email us at newseditor@dotnews.com and follow us on Twitter: @LitDrop and @gintautasd.