Memo to would-be million-dollar political donors: You can stash those checkbooks again.

Proposals to do away with Philadelphia's campaign-contribution limits are on ice this morning, instead of being advanced in City Council's weekly meeting.

That's because Councilman Jim Kenney, whose efforts to ease or undo the limits had threatened to upend the mayoral campaign, threw in the towel late Tuesday night, saying he was tabling his efforts until after the May 15 primary.

The move thrilled self-styled reformers - one said there was "dancing in the streets" - as it emboldened City Council challengers and sent the fund-raising wizards of the mayoral race's four non-millionaires back to the drawing board.

Millionaire businessman Tom Knox used $2 million worth of television ads to zoom from unknown to second place in a recent poll. He has vowed to spend whatever it takes to win. His opponents, meanwhile, will have to live under the current giving limits: $5,000 for individuals and $20,000 for political committees.

A supporter of U.S. Rep. Bob Brady's candidacy, Kenney said he had not introduced the measure at Brady's behest. And, yesterday, he said any flak Brady might have been getting as a result of the effort had nothing to do with Kenney's about-face.

"I wanted to have a clearheaded discussion about this," Kenney said yesterday. "All of the reactions to it, however incorrect [they] might be about my motives, did not provide for that clear discussion on the policy issue."

The impact on Brady and the other mayoral candidates - State Rep. Dwight Evans and former Councilman Michael A. Nutter, who criticized Kenney's bills, and U.S. Rep. Chaka Fattah, who would not say where he stood on the measures - is unclear.

When Kenney first introduced his plan early this month, several people in politics said he and his 10 Council cosponsors were overreacting to Knox's quick jump in the polls.

The upshot of Kenney's short-lived effort to change the rules?

Not all that much, at least in the mayoral race, said veteran political consultant Larry Ceisler. He said the tabling of Kenney's bills did little to change the dynamic of the campaign.

"Would they rather have a couple million dollars more?" Ceisler said. "Sure. But it doesn't make much difference." He said Knox still had the personal wealth while the four other candidates still had longer resumes and better-known names - the sort of things that generate votes and, even within the current limits, draw financial donations.

Brady seemed to agree. "I'll be OK. I'm raising money. I'm on TV. I'm going as hard as I can under the limits," Brady said yesterday. "I always said I'd go under whatever rules they give me."

Fattah, who led Knox and everyone else in the recent poll, reiterated his request that Knox voluntarily agree to limit his own campaign spending - a suggestion that Knox has laughed off. Beyond that, Fattah would say only: "We're going to follow the rules."

The caps on donations in the mayor's race could still be undone by a pending legal challenge - but only if the courts rule before the May 15 primary.

Meanwhile, the natural rhythms of politics are taking over: Knox no longer occupies the unique position as the only candidate with ads on TV - and all the benefits that come with it. Brady joined the television advertising battle this week, and campaign sources say Evans will soon follow.

But if Kenney's decision preserves the mayoral campaign's status quo, it introduces a new dynamic into the simultaneous but less visible race for all 17 seats on Council.

Insurgents - who ordinarily have a hard time winning seats in a Council chamber that sees more incumbents depart via death or incarceration than as a result of electoral defeat - claimed partial credit for Kenney's retreat. Hours before his decision, 14 Council challengers gathered in City Hall to denounce the bills.

"We know we had a hand in it - that's the only reason there is a victory here," the Rev. Jesse Brown, an at-large candidate, rejoiced yesterday. "The current City Council now knows that their every action is being monitored by, particularly, the current candidates that are running for office."

"I believe they got the message," said Curtis Jones Jr., who is challenging Councilwoman Carol Campbell, a vocal proponent of Kenney's bill. Jones said the successful move to push back the bill convinced him that this year would feature "a perfect storm" against incumbents.

"I did see a couple of staffers come around to observe the press conference," he said. "They must have scurried back and told their various representatives that we were serious. I think this could be the genesis of a reform movement in City Council."

Nutter, who is touting his reformist credentials on the mayoral campaign trail, joined in the celebrating.

"I am overwhelmed by the support that we received from the public, those who signed our Web-based petition, watchdog groups, and other officials," he said in a statement. He said 1,500 people had signed the petition.

Likewise, Evans, who had written Council to criticize the effort and sent his spokesman to the challengers' rally in City Hall on Tuesday, pronounced himself pleased with Kenney's move.

"It was a ridiculous discussion to have 90 days before the election," said Evans spokesman Tim Spreitzer.

As for Brady, he, too, acknowledged the self-inflicted wound caused by Kenney's bill.

"I saw him last night and I told him he should" pull the bill, Brady said yesterday in an interview. "I told them it would harm them. I said, 'You guys are getting too much heat.' I don't want good Council people to go down because of this. I agree with him - he's just trying to make the field level. But it's the wrong time."

Along with the would-be challengers, Kenney's Council colleagues were cooling to the idea in a hurry. Although his initial effort had 10 other cosponsors, a number of Council members had backed away as criticism of the effort mounted.

Contact staff writer Michael Currie Schaffer at 215-854-4565 or mcschaffer@phillynews.com.

Inquirer staff writers Marcia Gelbart and Patrick Kerkstra contributed to this article.