Mayor Bloomberg upped the ante for political candidates yesterday by urging some of New York’s wealthiest movers and shakers to write checks only to those who support his agenda items.

During a lunch at the Four Seasons Restaurant in Midtown, Mr. Bloomberg gathered about 100 high-powered political donors, outlined his state and federal funding priorities, and appealed to them to advocate on the city’s behalf when state and national candidates come knocking.

“There is nothing partisan about this,” Mr. Bloomberg told reporters after the lunch. “This is both sides of the aisle, or people who are not affiliated with a party at all. If you get elected and you want money from us, you’re going to have to deliver.”

Political scientists, saying the gathering was an unprecedented move for a mayor, viewed it as an innovative and high-stakes attempt to break the partisan gridlock that has stalled legislation in Albany and Washington.

Mr. Bloomberg made his plea in the poolroom of the Four Seasons, where guests such as investment banker Steven Ratner, a Republican fund-raiser, Georgette Mosbacher, and publisher Mortimer Zuckerman were served crab cakes as part of a four-course meal.

Along with his verbal appeal, the mayor gave out a wallet-size card with the words “Member Since 06” on the front and five priorities he has long been lobbying for listed on the back: a $2 billion federal tax credit to go toward the construction of a rail link between Lower Manhattan and John F. Kennedy International Airport; threat-based homeland security money; the ability to use eminent domain in blighted communities; an increase in the number of charter schools, and financial incentives to produce affordable housing.

Mr. Bloomberg, a billionaire who spent nearly $85 million of his personal fortune on his re-election, said if candidates are going to rely on New York City donors for vast contributions they owe it to city residents to fight for their causes.

He said residents in six city ZIP codes contributed $61.5 million to federal campaigns in 2004, with more than $22 million coming from one ZIP code on the Upper East Side, where his brownstone is located.

When asked whether Mr. Bloomberg’s appeal amounted to an unethical quid pro quo, which would be in conflict with federal election law, one civic leader said he didn’t believe so.

“I don’t think there’s an ethical issue here,” the president of the Citizens Union, Dick Dadey said. “The mayor is playing smart politics. It’s a strong-arm tactic, but one that people are clearly voluntarily agreeing to partner with him on. What he’s done is he’s asked his friends help him advance an agenda and they’ve done it willingly and openly.”

Mr. Dadey, whose organization supported Mr. Bloomberg in the last election, said demanding support for a specific project and making a donation contingent on that is questionable. But he said the mayor is really saying donors should close their checkbooks except for candidates who are supporting city issues.

“It’s a fine line, they are coming up against it, but I don’t think that they’re crossing it,” Mr. Dadey said.

The aggressive tactic could, however, further isolate Mr. Bloomberg, a Republican, from candidates and elected officials in his own party, whom he has already butted heads with.

Mr. Bloomberg defended the strategy, saying: “That’s what representative democracy is all about.”

While he has made sizable donations to the Republican National Party, he also has publicly fought with individual members of Congress and the state Legislature when they did not deliver for the city.

Most recently Mr. Bloomberg has threatened to back candidates taking on Republican state senators who he felt were not squarely onboard with giving the city more money for schools.

In 2003, Mr. Bloomberg feuded with Rep. Thomas DeLay, who at the time was the House majority leader, and with Rep. Harold Rogers, a Republican of Kentucky who was chairman of a subcommittee on homeland security. The mayor publicly said New Yorkers should reconsider before making political donations to Mr. DeLay, who was backing a transportation bill Mr. Bloomberg believed would short change the city.

According to published reports, the mayor donated $5,000 to Mr. Rogers’s congressional campaign, but grew upset when the lawmaker opposed a bill that would have divvied up security aid to cities based on threat level.

A spokesman for the National Republican Congressional Committee, Ed Patru, said yesterday that most donors already focus on issues that are close to home. “Most political donors contribute to candidates or causes they believe in and typically those tend to be close to home geographically,” he said.

He also said that Republican donors, “whether you live in New York or in Nebraska or California,” are largely motivated by a desire to keep President Bush’s tax cuts permanent.

The guests at the lunch received Mr. Bloomberg’s plea with open arms. Mr. Ratner said that while there might be resistance from the candidates looking for cash, he will stand up and make the city’s priorities known.

Political observers said Mr. Bloomberg’s move is bold, but that they are not convinced it will change the way money flows.

“Not even the governors of New Hampshire and Iowa have thought of that one,” a University of Virginia political scientist, Larry Sabato, said.

“You’ve certainly got to salute him for his creativity,” Mr. Sabato said, but he questioned whether most people would actually follow through.

“I love the wallet cards,” he said. “That’s brilliant. It’s amusing, but it might be effective.”

Mr. Zuckerman said it remains to be seen whether the tactic would work: “The people in this room have very unique conversations.”

Joshua Steiner, a founding Managing Principal of Quadrangle Group, a private investment firm, and Donald Marron, the head of Lightyear Capital, a private equity investment firm,paid for the event, a spokesman for the mayor said.