With the election days away, outside groups supporting Annissa Essaibi George’s mayoral bid raked in six-figure donations as Michelle Wu, Essaibi George’s rival, sought to block one of their ads from airing on television, calling it false and defamatory.

New Balance chairman Jim Davis, a top GOP donor who has also donated to Democrats such as former Mayor Marty Walsh and local lawmakers, this week sent an influx of cash to the coffers of the “Real Progress Boston” super PAC backing Essaibi George. He donated $600,000, bringing his overall total to $1.095 million over the last two months.

The “Real Progress Boston” super PAC is chaired by former Boston police commissioner William Gross, who has starred in TV and radio ads praising Essaibi George while attacking Wu.

The super PAC is separate from the similarly named Essaibi George super PAC “Bostonians for Real Progress.” But on Friday, filings with state campaign finance regulators indicating one super PAC funneled money to the other: “Real Progress Boston” sent $220,000 to “Bostonians for Real Progress.” When asked for comment, George Regan, whose public relations firm is working for “Real Progress Boston,” said, “I have nothing to add.”

Super PACs can raise and spend unlimited amounts of money, but they are restricted from coordinating with candidates.

The donations come as “Bostonians for Real Progress,” which is funded by unions representing electrical workers and firefighters who support Essaibi George, plans to air a TV ad attacking Wu over the purchase of her Roslindale home.

The ad, which the super PAC says will start airing on Saturday on the major TV stations as part of a $200,000 buy, claims Wu got a “sweetheart deal” for the two-family house. Earlier this month, the Boston Globe reported that it had reviewed the deal and “found no evidence of inappropriate activity by Wu.” The newspaper confirmed she and her husband paid the market value.

An attorney representing the Wu campaign, Gerald McDonough, this week sent out a cease and desist letter to TV stations, saying the ad should not to be aired and noting that TV stations are prohibited from airing third-party and super PAC ads that are demonstrably false. (Candidate ads do not face the same restriction.)

The cease and desist letter notes that Wu and her husband bought the two-unit home together in 2015 with Wu’s college roommate and her husband. In 2016, Wu and her husband bought the second unit for $390,000, a market-rate transaction.

The legal counsel for “Bostonians for Real Progress” fired back in his own letter to at least one TV station defending the ad by claiming in part that Wu's family paid less than market rate. Steve Jewett, the super PAC’s executive director, said in a statement that “we have clearly hit a nerve with Wu.”

Wu spokesperson Sarah Anders said Bostonians “deserve better than cynical, dishonest smears” and called for the ad to be taken down. The ad has been circulating on Twitter through anonymous accounts.

“It’s sad but not surprising that those wishing to continue the status quo are choosing to spend the last days of this race peddling lies, rather than engaging voters on our most pressing issues, like housing affordability, quality schools, and the climate crisis,” she said in an emailed statement.

After the preliminary, Essaibi George asked for the super PACs to stay out of the race, while Wu said they should remain positive. The Essaibi George super PACs have ignored both requests.

Wu has her own super PACs — funded by environmental groups, attorneys and others — and their TV ads and campaign materials have so far stayed positive.

“Our campaign cannot speak to SuperPACs or coordinate with them,” Essaibi George spokesperson Molly McGlynn said in an emailed statement. “We can only answer for and speak to Annissa's vision and record. That being said, Annissa has been the only candidate who called for SuperPACs to stand down in this race.”