A political action committee backed by city labor unions has collected $2.7 million in support of Los Angeles mayoral candidate Wendy Greuel, making it the biggest independent PAC in the race.

Mayoral candidates Greuel and Eric Garcetti attacked one another over questions of integrity Monday during a debate sponsored by KPCC, NBC 4, Telemundo and USC.

At $2.7 million collected and counting, Working Californians to Elect Wendy Greuel for Mayor 2013 is the biggest independent political action committee in the mayor's race. A senior official describes it as a coalition of labor, business, and philanthropists, but city unions — particularly those representing Department of Water and Power workers — have given the lion's share of the PAC's money.

Attacking the PAC has become part of Councilman Garcetti's campaign mantra: "I don't have $3 million from a super PAC led by the DWP union supporting my campaign," he said in Monday's debate.

RELATED: KPCC's LA mayoral endorsement tracker

Garcetti asserts that unions representing DWP and other city workers are trying to buy the mayor's office for Greuel to preserve their pay and pensions.

Greuel has a ready response: "I have been independent, I've audited the Department of Water and Power. I have said we should look at the pensions of the Department of Water and Power."

Donors to Working Californians are mainly individual union members; the locals that have put up the most money for the PAC are Locals 11 and 18 of the  International Brotherhood of Electrical Workers and unions representing other DWP workers, such as pipefitters and plumbers.

Jose Alvarado is a journeyman electrician for IBEW Local 11. He said he's OK with the union funneling his political contributions into the mayor's race.

"It is very important," he says. "All it comes down to is how many jobs, what mayor will help us bring jobs to L.A."

City employee unions support Greuel because she's in the best position to preserve their jobs and benefits, says Working Californian's top strategist, Sean Clegg.

"Their real interest and stake in this election for Wendy Greuel is all about the fiscal health of Los Angeles and the impact of continuing bad practices on the life blood of the utility," he said, describing  Working Californians as a coalition.

"It's labor, it's also leading philanthropists and business community folks and some of the leading lights in Hollywood," said Clegg.

While there are contributions from business moguls such as Eli Broad and Steven Spielberg, city union workers like Jose Alvarado collectively have given three-quarters of the money Working Californians has collected.

As for spending, so far, most has gone to two ads.

A pro-Greuel ad declaring Los Angeles on the brink of bankruptcy and Greuel the only leader who can "clean up the mess at City Hall" cost Working Californians $1.24 million.  The group spent another $500,000 on a Garcetti attack ad using video of him singing an anemic rendition of "White Christmas."

"It's Christmas every day for Eric Garcetti," the narrator says. "As the city went through a recession, he was living large. ... Tell Eric Garcetti it's time to end the holiday at City Hall."  

Big difference 

Both candidates are pro-labor, but political analyst Jaime Regalado says one big difference sets them apart in the eyes of the city labor unions. Garcetti was on the city council over the past four years and had to cast votes the unions didn't like on budget cuts and employee furloughs.

"I'm not sure that Local 18 feels they can thoroughly trust Eric because, as council president, he guided much of the conversation that resulted in not only the furloughs but also the retrenchment that occurred in terms of pension discussions," Regalado said.

Regalado says Greuel — in the controller's office — was not forced to vote on those issues.

He says labor has become an important but divided force in this election, as city unions funding the Working Californians PAC back Greuel and non-city unions support Garcetti.

So who is Jose Alvarado — the electrician — choosing for mayor? Although his union backs Greuel, he's just not sure yet.

"You can't always take someone's opinion or advice just because you're a member," Alvarado said. "So that would be my homework to do a little bit more research on each individual."

In the end, political analyst Jaime Regalado says, the mayor's race may hinge on the choices made by Alvarado and his fellow rank-and-file workers.

What do you think of the influence of money from city labor unions in this election? Let us know in the comments below or on KPCC's Facebook page.