NEW YORK – The Secret Service clamped down on midtown Monday night to protect President Bush from a possible assassin armed with a hunting rifle.

Lawrence Ward, 59, left his upstate New York home Wednesday with a .30-30 lever-action hunting rifle in the trunk of his car, telling a neighbor, “I’m not coming back.”

Inside his house in Bainbridge was a picture of Bush with the words “Dead Man” spray-painted near it, law enforcement authorities said.

Bush was in town for a fund-raiser at the Sheraton New York before speaking Tuesday before the U.N. General Assembly.

The Secret Service deemed Ward, a software engineer, such a “credible threat” that a three-square-block chunk of midtown was cordoned off.

Secret Service agents and city cops patrolled the area looking for anything suspicious.

Ward’s ex-wife, Judith Ward, 59, who lives in Connecticut, told the Secret Service she thinks her former husband “is very dangerous and capable of killing someone and/or committing suicide.”

She said Ward “is obsessed with weapons, (Oklahoma City bomber) Timothy McVeigh and Stephen King’s book “The Dead Zone’ – a novel about the stalking and attempted assassination of a presidential candidate,” according to a Secret Service document.

The document, reviewed by the Daily News, said Ward sent his ex-wife a CD that mentions killing both Bush and Democratic rival John Kerry.

He also was said to be “obsessed” with his 19-year-old daughter, Priscilla Jane.

Reached by The News, Judith Ward said she divorced her husband four years ago after 18 years of marriage because “he was a wife-beater and other things I don’t want to talk about.” She said she feared for her daughter’s safety.

Lawrence Ward’s own brother warned that he has a “violent nature,” the Secret Service document said.

Authorities said Ward has a criminal past dating to 1991, including an indecent sexual proposal charge.

The neighbor in Bainbridge, a Chenango County community about 40 miles northeast of Binghamton, told authorities that Ward “frequently spoke of “fighting the system’ and other anti-government topics.”

The neighbor said Ward gave him the keys to his place and told him to take whatever he wanted. He then drove off in a blue 1997 Toyota sedan with New York license plate BRF-6546.

Two days later, the neighbor went into the house, found the photo of Bush and called police.