This union-friendly city is one of five finalists to host the event, and organizers want assurances there will be no labor conflicts during the convention to avoid any disruptions or embarrassing images for the Democratic Party, historically tied to organized labor.
"That's one of their concerns," said Patrick Eiding, who heads the Philadelphia AFL-CIO and who attended a breakfast Thursday with the visiting site selection committee. "They want to make sure there'll be labor peace."
If interunion disputes arise, Eiding said in an interview, "we'll fix it some other way besides putting a rat or cat out there."
He and other local labor leaders pledged that unions would put up at least $5 million toward the roughly $80 million the local host committee needs to raise from private sources to pay the expenses of holding the convention.
The potential for organized labor to get its nose publicly out of joint is all too familiar to DNC convention organizers. In 2012, union leaders were angry when the party held its convention in the "right-to-work" state of North Carolina, home to one of the least-unionized workforces in the United States. Many national unions declined to contribute to the Charlotte convention, and some union members protested near the site.
In 2000, when Philadelphia hosted the Republican convention, union members welcomed the GOP by wearing T-shirts that read "Republican for a week." Even so, there were reports that members of the Electricians union had disputes with media companies that wanted to set up their own equipment.
"Everybody has put aside all that for the good of Philadelphia and the region," John "Johnny Doc" Dougherty, the politically wired leader of Local 98 of the International Brotherhood of Electrical Workers, told The Inquirer on Friday.
"There won't be an issue," he said. "Labor leaders are professional and know the convention would bring plenty of work for everybody."
Indeed, the mere possibility that Philadelphia will get the convention may be producing some fringe benefits for labor.
The 8,800 blue-collar city employees represented by District Council 33 of AFSCME have worked for five years without a contract, and negotiations with the city had been at a standstill - until recently, the union's leader said.
Municipal workers have had rocky relations with Mayor Nutter, who has sought deep concessions on work rules and benefits, and who has been dogged by union protests. Last year, Nutter was unable to give his budget speech because of protests in the City Council chamber. After trying to get courts to impose contract terms, the administration eventually settled with some of its unions - but not with its biggest, D.C. 33.
City Council President Darrell L. Clarke - who termed the situation "ridiculous" and unfair to a union that includes sanitation and streets workers who won wide praise during the brutal winter - said the wooing of the DNC offered an opportunity for settlement.
"One way to make sure we're viewed as a labor-friendly venue for the convention," Clarke said, "is to give these people a contract."
Pete Matthews, president of D.C. 33, said that there was a negotiating session Aug. 8 and that the city was receptive to considering union proposals for saving on benefits.
"This is the first movement we've seen from the city in a long time," Matthews said. "I absolutely believe it can be worked out with common sense and fairness."
Councilman James Kenney noted that by the time the convention happens, Philadelphia would have a new mayor. "I don't know if they can get a contract until [Nutter] is gone," said Kenney, who is considering a run for the job. "By the time the convention rolls around, whoever's mayor can get it done."
By comparison, Brooklyn, N.Y., seen as Philadelphia's fiercest rival for the convention, has enjoyed a degree of labor peace in recent years. New York City Mayor Bill de Blasio was elected last year with strong union support - and hasn't been in office long enough to lock horns with his city's municipal unions. Of course, if the DNC does pick Philadelphia, there are still two years to try to work out the tangled dispute at the Convention Center, a slow brawl that pits the Metropolitan Regional Council of Carpenters and the International Brotherhood of Teamsters against the center's management and four other trade unions working there.
The Carpenters and Teamsters had delayed signing on to new work rules designed to make exhibitions less expensive and smoother for customers at the center. Eventually, they agreed to the terms - but the center's management barred them and handed the work to two other unions.
To be sure, Carpenters picket lines and the inflatable cat might become a less frequent sight outside the Convention Center. A mediation meeting on the dispute is scheduled for next month before the state Labor Relations Board, said Marty O'Rourke, spokesman for the Carpenters.
"We're going into that meeting with good intentions, and we hope that management is, too, and that we can work out a reasonable solution," he said. "The carpenters fully support the DNC coming here."
Inquirer staff writer Jane M. Von Bergen contributed to this article.