One of Mr. Paterson’s preferences had been to select a woman to replace Mrs. Clinton.

The governor continued to deliberate and discuss the matter with his advisers  despite earlier reports that he had settled on Ms. Gillibrand  until he made his decision, according to the person who talked to him. He then called Ms. Gillibrand, who had earlier in the evening been told to come to Albany to await an announcement, to let her know she was his pick.

If Mr. Paterson was hoping to quiet the tumult over the selection process by picking Ms. Gillibrand, there were indications that he may not get his wish. Ms. Gillibrand, who has been endorsed by the National Rifle Association, is controversial among some of the party’s more liberal leaders downstate.

Representative Carolyn McCarthy, a Long Island Democrat and ardent gun control activist, said Thursday that if Ms. Gillibrand got the job, she was prepared to run against her in a primary in 2010. Ms. McCarthy was elected to Congress after her husband was killed in a gunman’s rampage on the Long Island Rail Road in 1993.

Ms. Gillibrand’s selection was a careful political calculation by the governor, who will run for his second term as governor in 2010, when Ms. Gillibrand will also be on the ballot. The choice reflects Mr. Paterson’s thinking that his selection should be someone who can help him attract key demographics  in Ms. Gillibrand’s case upstate New Yorkers and women.

Image Representative Kirsten Gillibrand with Robert Barton, a dairy farmer, at a town hall meeting in Milford, N.Y., in May 2007. Credit... Nathaniel Brooks for The New York Times

Ms. Gillibrand, who lives near Hudson, N.Y., just outside of Albany, with her husband, Jonathan Gillibrand, a financial consultant, and their sons, Theodore, who is 5, and Henry, who is 6 months old. (Ms. Gillibrand received a standing ovation on the floor of the House from her colleagues for working right up to the day she gave birth to Henry.)