For a guy who says he despises Mayor Rahm Emanuel, William J. Kelly has given a big boost to the mayor’s re-election bid.

The Republican gadfly and perennial candidate had said he would challenge Emanuel and said he contributed more than $100,000 last month to his campaign to unseat the mayor.

But on the final day of candidate filing last week, Kelly said he wouldn’t run after all.

Kelly has run for other offices and lost badly. His chances were even slimmer against Emanuel. He reported receiving only one other campaign contribution, for $1,000.

OPINION

Yet, the money Kelly reported giving himself has greatly altered the race he’s now abandoned. Under Illinois law, if any candidate contributes $100,000 to their own campaign for mayor, the caps on contributions are removed for all the candidates in the race.

Normally, they would be prohibited from accepting more than $5,300 from an individual, $10,500 from a company or $52,600 from a political action committee. No longer, thanks to Kelly.

The big beneficiary, of course, is Emanuel, a master fund-raiser who shattered the mayoral campaign spending record in his first run for the office four years ago.

The law that established the caps took effect on Jan. 1, 2011, in the middle of the race to succeed the retiring Mayor Richard M. Daley. Emanuel used the time before the caps went into effect to build a huge fund-raising lead over his rivals in the February 2011 election.

This year, the release from caps has helped Emanuel quickly expand his already-vast advantage over the nine challengers who filed nominating petitions to appear on the ballot.

Even though Kelly withdrew, there will be no limit on how much contributors can give, says Ken Menzel, deputy general counsel for the state’s board of elections.

“I think the cap is off for at least the February election,” he says.

If no candidate wins more than 50 percent of the vote in February, forcing a runoff in April, then the caps might be enforced again. Or maybe not, Menzel says.

It’s uncertain, Menzel says, because state officials aren’t sure what to do.

“The caps went into effect in 2011, and we haven’t had a chance to litigate and work our way through the nuance,” Menzel says. “Nobody expected someone to throw $100,000 into his campaign and not run.”

On Tuesday, the guy who did that sent me what he says is a bank statement from his campaign account showing that it received a deposit of $100,000 last month. Kelly didn’t provide proof of where the money came from but said he wrote himself a six-figure check.

“It was actually acquired through hard work,” he says of the money.

Kelly could take it back. But he says he instead plans to spend it to create “a real Republican organization” for Chicago.

The lack of support from such a group, he says, was why he dropped out of the race. Never mind that there hasn’t been a Republican Party organization in any real sense in Chicago for generations.

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Kelly says he didn’t mean to help Emanuel after years of criticizing the mayor, even hounding him at public appearances.

“Rahm Emanuel already had more than enough money to pay for a first-class, gold-plated campaign,” Kelly says.

Lifting the caps, he says, also gives other candidates a chance to take large contributions.

At least one of Emanuel’s rivals appears to be taking advantage of the new fund-raising rules.  Cook County Commissioner Jesus “Chuy” Garcia’s campaign spokesman said the Service Employees International Union Healthcare is kicking $250,000 into Garcia’s fund.

But Garcia still favors the caps, because he doesn’t expect his supporters in labor will be able to remotely match what Emanuel is raising from his wealthy friends.

It might be awkward for election officials to reimpose caps after they’ve already told the candidates to raise and spend money without the limits in place.

But the best chance for Emanuel to face challengers on a more even playing field is for somebody to try to get the contribution caps reinstated, by filing a complaint with the state election board.

If this is a loophole in the campaign-finance rules, state lawmakers should act to close it before somebody else pulls a William J. Kelly and again makes a mockery of the law.