"I would ban the horse carriages in Central Park within the first week on the job," de Blasio told a midtown forum Tuesday night sponsored by several Democratic progressive groups.
"I think it's horrible what happens to the horses. I think it's unnecessary and doesn't do anything for our economy, much to the chagrin of the mayor who thinks it's at the center of our tourism economy."
It happens that one of the four-legged industry's most reliable supporters is City Council Speaker Christine Quinn, a major de Blasio mayoral rival who has resisted insistent demands by animal rights activists to replace the horses with antique motor cars.
A Quinn spokesman said her position hasn't changed -- she wants as many protections as possible for the horses, but won't support putting them out to pasture.
Bill Thompson, another leading mayoral contender, is on deBlasio's side.
Longshot candidate Sal Albanese is taking the bridal path down the middle.
"There are legitimate concerns on both sides here," he said. "The animals deserve humane care and the drivers deserve job security."
In addition to jumping on the horse issue, de Blasio has been hammering Quinn for refusing to enact legislation requiring private employers to provide paid sick leave.
Polls indicate he's not making much headway with that line of attack. Quinn maintains a large lead over all four Democratic rivals.
De Blasio allies say they're not worried by the numbers because most voters don't focus on the mayor's race until summer.
As evidence, they point to de Blasio's run against Mark Green for Public Advocate in 2009.
A Quinnipiac University poll issued June 17, 2009 gave Green 35 percent to de Blasio's 10 percent. The two finished neck-and-neck in a multi-candidate field in the primary. In the runoff two weeks later, de Blasio smashed Green 62 to 38 percent.
Not everyone trying to stop Quinn is as certain she'll collapse on her own.
One progressive Democrat is trying to line up an independent expenditure to pay for negative TV ads aimed squarely at Quinn.
"You'll see some spending before the end of the month," he predicted.
By David Seifman