(CNN) New York Gov. Andrew Cuomo on Sunday denied any prior knowledge of a mailing sent by state Democrats suggesting his primary challenger, Cynthia Nixon, would not support Jewish communities in the face of anti-Semitism.
The New York State Democratic Committee, which is effectively controlled by the two-term governor, paid for the flier, which falsely claimed Nixon supports the Boycott, Divestment, Sanctions (BDS) movement, which aims to pressure Israel over its treatment of Palestinians, and accused her of being "silent on the rise of anti-Semitism."
Nixon, who condemned "the rising hate crimes we are seeing against Muslims, Jews and many other communities" as recently as late August, slammed the mailing in a statement on Sunday, calling it "an attack not only on my children and my character, but on all New Yorkers."
"The accusation that my family promotes anti-Semitism is deeply, deeply offensive," said Nixon, who is raising her two older children in the Jewish faith and attends a New York City synagogue.
She then turned her attention to Cuomo and the state party, accusing them of employing "Trump-style divide and conquer tactics."
At a press conference on Sunday, Cuomo distanced himself from the message -- calling it "wrong" -- and criticized the state party's "approval process" ahead of its printing and distribution.
"I didn't know about the mailer," Cuomo said. "I heard about the mailer. I haven't seen the mailer. The way I ran this campaign, it's been on the issues, it's been positive. I think the mailer was a mistake. I think it was inappropriate."
The clean-up efforts began a night earlier, when Geoff Berman, the state party executive director whose firing Nixon called for on Sunday, tweeted an apology.
"Let me be very clear: This mailer was a mistake and is inappropriate and is not the tone the Democratic Party should set -- it will not happen again," he wrote.
Berman also denied having signed off on it, and when asked who did, replied: "I'm not going to get into internal HR details on Twitter but the people involved are being held accountable. Believe me, we take this seriously."
As Cuomo began speaking on Sunday, Berman tweeted again to announce that the party "will work with the Nixon campaign to send out a mailing of their choosing to the same universe of people" targeted by the initial, controversial mailer. It's unclear what form that will take.
New York City Mayor Bill de Blasio, who on Saturday made it official that he would not endorse a candidate in the gubernatorial primary but has a notoriously testy relationship with Cuomo, condemned the flier's message on Twitter.
"The mailer sent by the NY Democratic Party in the 11th hour falsely attacking Cynthia Nixon is beyond unacceptable -- it's downright Trumpian," de Blasio said. "A tweeted 'apology' calling it a 'mistake' is laughable. The state party must compensate the Nixon campaign immediately."
The furor, heightened by its proximity to Thursday's primary, extended beyond the typical bounds of what has been a heated contest between Cuomo, who has the support of Hillary Clinton, former Vice President Joe Biden and the national party establishment, and Nixon's insurgent progressive challenge, which has been backed by the progressive grassroots advocacy group Indivisible and multiple New York-based chapters of the Democratic Socialists of America.
On Saturday night, Rabbi Sharon Kleinbaum of Congregation Beit Simchat Torah -- where Nixon is a member — and her wife Randi Weingarten, president of the powerful American Federation of Teachers, issued a statement on Facebook condemning the ad as "beyond the pale" and full of "distortions."
"While we have come to expect this kind of baseless smear from the GOP and from Trump, this is not who our country or our state or our party should be," they wrote. "It's good that Governor Cuomo has renounced it tonite."
Cuomo leads his race with Nixon by more than 30 percentage points, according to the last available public polling, which was conducted in July. But he has spent heavily through its final weeks, including an outlay of more than $8 million during a three-week stretch in August, when Nixon's campaign, which has not aired a single television ad, spent only about $450,000