Fifty-seven percent of Iowa adults disapprove of the way New Jersey Gov. Chris Christie (R) has handled the bridge scandal plaguing his administration, according to a new Des Moines Register poll.

That compares to just 18 percent who approve of the way Christie has handled the scandal, in which emails show his then-deputy chief of staff ordered closures to access lanes to the busy George Washington Bridge.

The numbers for independents are also bad for Christie, with 60 percent disapproving and 22 percent approving. Republicans disapprove slightly less, by a margin of 47 percent to 34 percent.

Iowa Republicans will be a crucial bloc if Christie runs for president in 2016, as is widely assumed. They caucus in the country’s first nominating contest.

The Democratic-leaning PPP poll put Christie in fourth place, with 10 percent, in the Iowa Republican field at the end of February. He trailed former Arkansas Gov. Mike Huckabee, at 17 percent, Sen. Rand Paul (Ky.), at 14 percent, and former Florida Gov. Jeb Bush, at 13 percent.

The New York Times reported Monday that federal prosecutors are now investigating David Samson, the chairman of the Port Authority, which oversees the bridge, for potential conflicts of interest. Samson is a close ally of Christie.