John Kerry (search) and Thomas Menino (search) might normally be cooing at one another right now — the Democratic presidential candidate and the Democratic mayor of the city that will host the national convention this summer.

But not those two.

"Small-minded and incompetent" was how Menino described the Kerry campaign recently when the four-term Massachusetts senator canceled a speech in Boston rather than cross a police union's picket line.

Then there's the matter of the phone call. Kerry's aides say the mayor hung up on the nominee-in-waiting, who had called to discuss the union dispute.

Menino denies it, and says his wife will back him up on it.

Whatever.

The public dispute has tarnished the luster of the convention that Menino and Massachusetts Sen. Edward M. Kennedy (search) worked so hard to bring to Boston, and that will award Kerry the presidential nomination in four weeks.

Menino has been trying to reach agreement with Boston's police officers' union, which has been without a contract for two years. National Democrats expected the mayor to settle the issue and other labor disputes long before the convention, which begins July 26.

But earlier this month, protesting officers delayed contractors working on the FleetCenter sports arena, site of the convention, and they picketed the U.S. Conference of Mayors meeting on Monday.

When Kerry refused to cross the picket line to speak to the mayors, Menino engaged in some name-calling. "He was disturbed by it and, I think more than that, he was hurt," said Trenton, N.J., Mayor Douglas Palmer, president of the National Conference of Democratic Mayors.

On Wednesday, he tried to play down the controversy, saying his frustration was with Kerry's staff, not the candidate.

"I talked with the campaign today and there's no issues that will really stop me for working for John Kerry," Menino said. "I'm more angry about the rumor. Why would they start rumors like that? It's ridiculous. There's too many things we need to do."

The Kerry campaign said they understand what a mammoth task Menino faces with the union dispute and the prospect of thousands of visitors descending upon the city in less than four weeks.

"We have friends on both sides of the city dispute and we hope that they're able to work it out to their mutual satisfaction," said Kerry campaign spokesman Michael Meehan. "John Kerry's looking forward to accepting the nomination in his hometown."

A spokesman for Kennedy said the senator "is doing all he can behind the scenes" to smooth things over between Kerry and Menino.

While Democratic leaders and officials were scrambling to bring peace to Boston before the convention, many said there was little that could be done to force a mayor to reach a contract agreement with one of his unions.

Democratic officials have little leverage to force Menino's hand, especially since the mayor has indicated that he is not interested in higher office.

"If the nominee were from another state, Menino wouldn't feel as betrayed by what he did," said Lou DiNatale, a political science professor at the University of Massachusetts-Boston. "But the nominee is from here and he knows Tom Menino and he knows the police union and there's expectations on all sides about how he should behave."