TRENTON, N.J. ? In a stunning declaration, Gov. James E. McGreevey announced his resignation Thursday and acknowledged that he had an affair with another man. “My truth is that I am a gay American,” he said with his wife by his side at a nationally televised news conference.

“Shamefully, I engaged in adult consensual affairs with another man, which violates my bonds of matrimony,” the twice-married father of two said. “It was wrong, it was foolish, it was inexcusable.”

McGreevey, a Democrat, said his resignation would be effective Nov. 15.

McGreevey, 47, refused to answer questions at the Statehouse news conference. He said “it makes little difference that as governor I am gay,” but added that staying in office and keeping the affair and his sexual orientation secret would leave the governor’s office “vulnerable to rumors, false allegations and threats of disclosure.”

“Given the circumstances surrounding the affair and its likely impact upon my family and my ability to govern, I have decided the right course of action is to resign,” he said without elaborating on what the circumstances were.

Two sources close to McGreevey, both speaking on condition of anonymity, said the man involved in the affair was Golan Cipel, an Israeli poet who worked briefly for the governor as a homeland security adviser despite having no security experience.

One source, a senior McGreevey political adviser, said Cipel threatened McGreevey several weeks ago that unless he was paid “millions of dollars,” Cipel would file a lawsuit against the governor charging him with sexual harassment.

That source said a lawyer for Cipel “indicated that should the money be paid, Cipel would disappear until after the 2005 election.”

The second source, a high-ranking member of the McGreevey administration, said Cipel made several threats about a lawsuit and demanded “an exorbitant sum of money to make it go away.” Cabinet members and administration officials learned of that threat Wednesday night, the official said.

New Jersey Gov. James. E. McGreevey announces his resignation during a news conference at the Statehouse, as his wife, Dina Matos McGreevey, listens.

A phone number for Cipel could not immediately be found, and he could not be reached for comment.

Senate President Richard J. Codey, a Democrat, will become acting governor and serve out the remainder of McGreevey’s term, which ends in early 2006. If McGreevey were to leave office before Nov. 15, a special election would be held.

Former Republican Gov. Christie Whitman said McGreevey “made a courageous decision” but criticized his plan to wait until Nov. 15 to leave office, saying it “smacks of politics.” She said it “would be in the best interests of the state” for the governor to step aside immediately.

Rumors had been circulating for several years that McGreevey was gay, reaching the level of open hints on New Jersey talk radio shows.

A Roman Catholic, McGreevey had a daughter with his first wife, Kari, who lives in British Columbia with the child. He has another daughter with his current wife. McGreevey spokesman Micah Rasmussen declined to answer any questions about the future of McGreevey’s marriage.