Allies of Bill Peduto are bracing for what they expect will be a negative attack, launched by an independent political committee whose finances are murky, but appears to have ties to Mayor Luke Ravenstahl.

At 10:30 last night, Peduto's campaign sent out a blast e-mail to supporters, advising them that "For the first time in Pittsburgh's history, an outside, secret group is funding attack ads in the mayoral election. Starting tomorrow, a group backed by Wagner & Ravenstahl has purchased TV time to begin running a smear campaign against Bill Peduto. The Wagner-Ravenstahl group -- which calls itself 'The Committee for a Better Pittsburgh' -- has kept their donor list from this year a secret."

Indeed, City Paper has discovered records indicating at least one ad buy organized by the committee. The group apparently intends to spend $1,600 on a commercial running on WPGH-53 sometime this week, perhaps as early as tonight. (UPDATE: I reworded the previous sentence to reflect the fact that the ad is apparently only slated to run twice during the next few days.) The 30-second spot will air during reruns of Two and a Half Men and Big Bang Theory, as well as the station's 10 o'clock news. (ADDED: The file also suggests that the agency placing the ad is SRCP Media, which bills itself as a "Republican media consulting firm" with clients that include Swiftboat Veterans for Truth, Mitt Romney, and Mitch McConnell.)

It is unclear where that money would be coming from. As we first noted a year ago, Mayor Luke Ravenstahl's campaign loaned the Committee $20,000 in April 2011, when the organization was established. Ravenstahl campaign records show that $17,000 was returned later that year. And in its 2012 annual report, the Better Pittsburgh committee reported returning another $2,000 of that money, leaving it with an outstanding debt of $1,000 to Ravenstahl's campaign, and just $121.43 in cash.

The report showed no other activity, and no other reports were available online from the state. But campaign-finance records suggest that the committee's treasurer, John R. Morgan, also serves as treasurer for the campaigns of state Sen. Jim Ferlo, an ally of Ravenstahl who has endorsed Wagner in this year's mayoral race, and state Rep. Adam Ravenstahl, the mayor's brother. A John R. Morgan also appeared in a 2008 Post-Gazette story about public employees landing on their feet with help from the Ravenstahl administration, though I haven't been able to verify if it's the same guy.

State records do not show contact information for the Better Pittsburgh campaign beyond a Downtown post office box. I left a message for Morgan at the Pittsburgh Water and Sewer Authority, which is where the P-G reported him working. I've also called and e-mailed the Ravenstahl campaign. When and if I get a response, I'll post it here.

Of course, the Better Pittsburgh ad has not aired yet, and for all we know, it's a loving portrait of a city and all the candidates who hope to lead it. But it's probably no surprise that Peduto's campaign is assuming that Ravenstahl is backing an effort to attack him. As we first reported in early March, when Mayor Luke dropped out of the race, he still had upwards of $1 million in a bank account. And "[n]othing in city law prohibits independent expenditures of money: Ravenstahl could, for example, set up a committee to spend untold sums attacking Lamb and Peduto." Independent expenditures are of course valid, if lamented, at the state and federal level, and nothing in the city's campaign ordinance bars them either. (Even it if did, a judge has said the rules don't apply to this year's mayoral race anyway.)

Bear in mind, however, that nothing is certain here. The next campaign-finance reports won't be released until May 10. We may not have a full accounting of the committee's finances until that point. Or later.

Stay tuned.