CHICAGO (CBS) — It’s no surprise that money is powering Chicago’s mayoral runoff.

But money from where? CBS 2 political reporter Derrick Blakley is taking a close look at who’s giving Toni Preckwinkle and Lori Lightfoot their campaign cash.

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Long before the mayoral race, Toni Preckwinkle has been a vocal backer of the Service Employees International Union, the SEIU.

“We can’t say because you clean an office building, you don’t deserve a living wage,” said candidate Toni Preckwinkle back in 2015.

Now, in the mayoral race, a spokesperson for Preckwinkle said:

“Unlike lawyer Lori Lightfoot, who has given her campaign hundreds of thousands of dollars, Toni is relying on grassroots support from all over Chicago.”

We’d say, that’s partially false.

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Lightfoot has been her own biggest contributor, donating $266,000 to her campaign. But various factions of the SEIU have poured in more than 3.2 million dollars for Preckwinkle.

That’s roughly 42 percent of her overall fundraising. Hardly a reliance on grassroots money. So, how have things changed since both candidates reached the runoff?

Lightfoot reported an influx of $387,000, some of it from big money donors:  Lawyer Leslie Bluhm, $100,000. Ad man Dale Taylor and retiree Peter Phillips, $50,000 each. But also: $105,000 from individuals, mostly amounts of $1,000 to $5,000.

And $71,000 from attorneys, mostly $1,000 to $5,000 amounts.

The people who’ve supported me are people that, frankly, are my friends who’ve known me since I was a baby lawyer and the kind of work and the integrity that I bring to the job of being a lawyer. So it’s a natural thing for people who know you, and like you, to be supportive,” said Lightfoot.

And Ald. Scott Waguespack (32nd) also contributed $10,000 to Lightfoot. Meantime, since reaching the runoff, Preckwinkle has reported a modest $6,500 in contributions, including $2,000 from her political director, $1,500 from a PAC and $3,000 from three individual donors.

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Overall, Preckwinkle has outraised Lightfoot by almost three-to-one. And while Lightfoot’s surge has already brought in an influx of cash, the big corporate and business money is still on the sidelines, at least for now.