Nixon has hammered Cuomo for failing to address New York City's beleaguered subways and for not following through on pledges to address corruption.
Now the New York Times reports that the flier was drafted and approved by two men with close ties to Cuomo.
Nixon says both groups were overlooked on 9/11.
Making a pit stop at the Upper West Side eatery on Sunday while on the campaign trail, Cynthia Nixon ordered a cinnamon raisin bagel with lox and capers.
Still, Democratic strategist Hank Sheinkopf said Mr. Cuomo was given a gift when Ms. Nixon ran too far to the left. The email also includes mentions of the governor's accomplishments on Jewish causes, which were also detailed on the flier.
In an interview with Reuters last week, Nixon said: "I feel people are going to be very surprised on Thursday", and cited victories she felt her campaign had already scored. After a slow start, she attracted money and endorsements - including a New York Times endorsement that is front and center in all of her advertisements. "But I love her and think if anyone is inclined voting Nixon is cool".
One of the candidates in the Democratic primary, Zephyr Teachout, pledged this week to investigate Mr. Cuomo should she win.
"To be informed about Andrew Cuomo is to want a change", she said. She would also be called to account for her idiosyncratic taste in bagels, and her support for a British tea shop frequented by her former co-star Sarah Jessica Parker.
"He is going hard, but I think what that shows is that he is actually scared because he understands that we've got a real hunger for progressive change in NY state and he doesn't have a record to run on", Ms. Nixon said Wednesday on the "Breakfast Club" radio show.
The Cuomo campaign released a statement largely confirming The Post's reporting on the issue - while claiming Schwartz somehow missed the "negative section" of the mailer before giving the green light to distribute it.
While Cuomo has inveighed against President Donald Trump's policies repeatedly, the anti-Trump wave of progressive engagement has created a disconnect between Cuomo's record, which is fairly moderate, and the feisty attitude of the current Democratic base. Dealing with state corruption was the only issue that likely Democratic primary voters saw Nixon doing a better job on than Cuomo in the September 10 Siena poll, 42-39 percent.