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.

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.

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.

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.