Mayor Rahm Emanuel padded his huge fundraising lead by $520,900 over the last week, thanks, in part, to hefty contributions from the La Salle Street exchanges whose transactions his challengers want to tax.

Emanuel has argued repeatedly that the so-called “La Salle Street tax” is not only prohibited by state and federal law. But it also would be a huge mistake because the exchanges could leave Chicago, turning the financial district into a ghost town.

Still, Chicago Teachers Union President Karen Lewis has championed the transaction tax as a potential solution to the pension crisis looming over city government and Chicago Public Schools.

County Commissioner Jesus “Chuy” Garcia, who ran for mayor after a brain tumor forced Lewis to take a pass, has said a transaction tax ought to be considered. Mayoral challenger Bob Fioretti (2nd) has gone even further than that.

Emanuel’s already brimming campaign war chest is continuing to be the beneficiary.

The mayor’s latest campaign disclosure statement includes $20,000 from the Chicago Board Options Exchange and $10,000 apiece from CTC Trading Group, Chicago Financial Access LLC, X-Change Financial Access LLC and the Options Clearing Corp.

Other big donations to the mayor in the last week include: $50,000 from Matthew Pritzker; $55,000 from Robert Loquerico; $50,000 apiece from Roger Altman, Chicago Journeymen Plumbers Local 130 and Emerson Collective LLC; $25,000 from Jeff Blau and Stephen Ross and $20,000 from David Bunning.

U.S. Rep Luis Gutierrez (D-Ill.) gave Emanuel $30,000.

Gutierrez and the mayor were at loggerheads over immigration reform during Emanuel’s days as White House chief of staff. But they have since made peace to the point where Gutierrez is serving as co-chairman of Emanuel’s re-election campaign.

Days before former Mayor Richard M. Daley issued a one-paragraph endorsement of his successor, Emanuel also got $10,600 from Bill Daley and his wife, Bernadette Keller.

When Emanuel stepped down as White House chief of staff to run for mayor, he was succeeded by Bill Daley.

The $520,900 in new contributions bring to roughly $12 million the amount Emanuel has raised for his re-election campaign. Since 2010, the grand total is roughly $31.5 million.

Garcia said he is not surprised that Emanuel is continuing his frenzied fundraising or that La Salle Street exchanges keep filling the mayor’s campaign coffers.

“He’s really worried about a runoff. That’s why he continues to bring in money by the boatload. All of the monied interests want to avoid a runoff. They don’t want to avoid a transaction tax. They want to avoid a government that’s going to embrace all of Chicago and focus resources on the neighborhoods,” Garcia said.

Breaking into the popular Beatles song, Garcia said, “Can’t buy me love. Money can’t buy you love in Chicago any more.”

Last week, the nexus between Emanuel’s heavy-hitting donors and the mayor’s public appearances and official actions took center stage during a live mayoral forum on the WTTW-Channel 11 program, “Chicago Tonight.”

Fioretti pounced after moderator Phil Ponce asked about a Chicago Tribune investigation that concluded that half of Emanuel’s top 100 donors have received City Hall benefits ranging from contracts and permits to appointments and personal endorsements.

“$30 million, then all of these board appointments and look at those top 103 [donors]. Sixty of ’em received some kind of contract, some kind of benefit. If that’s not pay-to-play, I don’t know what is,” Fioretti said then.

Emanuel has argued that the millions he’s raised has not stopped him from standing up to big business — on issues ranging from affordable housing set-asides and raising Chicago’s minimum wage to taxing skyboxes and closing sales tax loopholes. Same goes for the labor unions that opposed him four years ago, but are now contributing heavily to his re-election campaign.

During an exclusive interview with the Chicago Sun-Times late last week, Emanuel said there is no quid pro quo or pay to play.

“I’ve taken on supporters. Their support for me is not about this permit or this license or this zoning.  This is about creating stability, managing the challenges the city faces and doing it with a sense of strength and leadership,” Emanuel said.

“They’re not getting anything. They don’t support what I’ve done on the minimum wage. They don’t support how I’ve cracked down on the housing piece and how I changed the way we do affordable housing. Did I not say to all the corporations that buy the skyboxes, `You’re not getting your little loophole anymore on the amusement tax?’”

Asked why he needs $12 million to get re-elected when his two strongest challengers didn’t run, Emanuel said, “Like I did for President Clinton and President Obama, I want people to know what we’ve done and what I’m going to do. I think that’s what campaigns are about.”

While Emanuel continues to raise money, millionaire businessman Willie Wilson keeps dipping into his own deep pockets.

Since Jan. 2, Wilson has contributed nearly $2 million to his own campaign, $530,000 of it in the last two weeks. Wilson has argued that self-funding is the only way to make certain he “owes nobody” any favors.