Less than a year after the New York Daily News endorsed Bill de Blasio for mayor with “worrying reservations,” after their preferred candidate, Christine Quinn, lost the primary, the paper’s relationship with the mayor has devolved to the point that they’re cursing at him on their front page. The Daily News posted a preview of Thursday’s cover, which features the headline “You’re an Ass, Mr. Mayor.” The paper launched a campaign in April to save Central Park’s carriage horses, which de Blasio wants to replace with electric cars. On Wednesday, more than 100 carriage-horse supporters dropped off sacks containing 40,000 signed petitions on the steps of City Hall. De Blasio enraged them further by sending an aide to pick up the bags, prompting the Daily News to hurl the somewhat horse-related pun. (Horses and donkeys are both members of the Equidae family.) Or maybe it’s a play on NYCLASS? Either way, it’s a bold stance.