So change that to “If you want to return to the days before Rudy, vote Democrat.” Leave the negative references implied.
Those offended would still call it "racist" because it's about the only way they can oppose it. And if they did go ballistic opposing that slogan, you could expect a full-fledged local MSM feeding frenzy to aid their cause, so much so that it would end up being a national cause celebre for the 'Rats.