“I fully recognize the severity of the situation and I am profoundly sorry,” Mr. Kolb said. “There is no excuse and no justification for what occurred Tuesday evening. I made the wrong decision, and it is one I deeply regret.”

Image Assemblyman Brian M. Kolb Credit... Ontario County Sheriff's Office

On Friday, Mr. Kolb announced that he was relinquishing his position as Republican leader.

“I have always tried to put the needs and best interests of our conference ahead of my own,” he said in a statement. “That is why I have decided to step down as minority leader.”

A spokesman for Mr. Kolb said separately that the assemblyman had no plans to give up his seat.

Mr. Kolb was driving his state-issued 2018 GMC Acadia just in front of his home around 10:30 Tuesday night in the town of Victor, N.Y., about 15 miles southeast of Rochester, when he drove into a ditch, the Ontario County Sheriff Kevin Henderson said.

Sheriff Henderson said one of his deputies, called to the scene by a passer-by, administered several field sobriety tests and then took Mr. Kolb to the county jail.

There, an alcohol breath test indicated that the assemblyman’s blood-alcohol content was over 0.08 percent, the sheriff said. Mr. Kolb was charged with driving while intoxicated, a misdemeanor, and released pending a future court appearance, the sheriff said, adding that no one was hurt and no other vehicles were involved in the crash.