In Joe Lhota’s last campaign ad, Mayor Giuliani said of his former deputy mayor, “It was Joe who kept the city running during 9/11.” That’s a hard claim to top, so on Monday the Republican mayoral candidate shot a little lower. “This primary election has become embarrassing … a circus,” declares the narrator of his latest commercial, over a collage featuring Bill de Blasio being arrested, Christine Quinn wearing rabbit ears, and Anthony Weiner … being Anthony Weiner. The newspaper quotes that follow don’t go into any depth about Lhota’s accomplishments, but the message is that only one credential really matters: The entire country isn’t joking about Lhota’s brazen sexual antics … so far, at least.