It’s looking like the fight over an otherwise hum-drum ballot measure has turned more interesting — and immensely personal.

The San Francisco Apartment Association, which represents landlords and usually spends its time fighting City Hall over housing issues, has poured more than $50,000 in recent weeks into the fight against Proposition A.

Yes, that Prop. A — the $500 million, nearly universally popular transportation bond that Mayor Ed Lee has staked his political future on and every single supervisors is backing.

Some of the money went toward two mailers sent out by a group called the San Francisco Taxpayers Association that claim the ballot measure authorizes a “billion-dollar blank check” and “could raise taxes on homeowners and renters.” The mailer is signed by a number of groups, including the Coalition for San Francisco Neighborhoods and the San Francisco Green and Republican parties.

It would seem the Apartment Association’s donation, however, has less to do with the details of the bond and more to do with Lee’s relationship — or lack thereof — with the group, which has been on the losing end of a litany of tenant-friendly laws coming out of City Hall in the past year, as well as the recently-approved “Airbnb law,” which the association joined tenant groups in opposing.

President Janan New said her group believes the mayor has developed his housing policies “in a silo,” only consulting with a handful of connected tech moguls and Chinatown activists, and that they have also lost faith in his ability to shape all city policy, including transportation.

She noted that several of the mayor’s tech investor friends, including Sean Parker and Ron Conway, have poured tens of thousands of dollars into supporting the measure — in all, the yes side has raised nearly $700,000.

“We have lost faith that this administration is able to lead the city, and if you look at the reasons why — you will see huge contributions by the tech industry into this (measure),” she said. “Something is broken, and until all parties are brought in to formulate policy through his leadership, we will oppose a continuation of this.”

For his part, Lee claims he’s baffled, saying the bond will pay for a wide range of road and transit improvements that would particularly benefit the property owners the Apartment Association represents.

“That particular infusion of money … must be for some insane political reason that probably I can’t even comment on because it’s so extreme,” he said. “I don’t know why they would have done that — it’s in the best interest of anyone in this city that involves themselves in real estate to take a look what whats going on.”

But the mayor wasn’t done there, insisting the measure wouldn’t raise property taxes and saying he is “scratching his head that anyone who calls themselves leaders in any industry would forego the opportunity,” of putting badly-needed money into the city’s transit and transportation system.

“The reality is we have a congested city and we have to have a better transportation system,” he said. “What about the $250 million in Proposition A we are willing to spend on pedestrian safety?”