Gov. David A. Paterson introduced a bill on Thursday to legalize same-sex marriage, vowing to personally involve himself in the legislative debate at a level that is rare for a chief executive in New York.

Throwing the weight of his office behind legislation that still faces considerable obstacles in Albany, Mr. Paterson said he would leverage the personal relationships he developed over two decades in the State Senate to see the bill voted on  and passed. The vote is expected to turn on the thinnest of margins in the Senate, and some advocates say Mr. Paterson’s direct involvement could prove pivotal.

At a news conference in Manhattan on Thursday, Mr. Paterson, a Democrat, invoked the abolitionist movement of the 1800s, the writings of Harriet Beecher Stowe and the Supreme Court’s Dred Scott decision to argue that New York had neglected civil rights for gays and lesbians for too long. “I’m putting a stop to it,” he said. “We have a duty to make sure equality exists for everyone.”

The announcement came amid growing activity around the country on same-sex marriage: Iowa and Vermont have legalized the practice in the past month, and the New Hampshire State Senate has been debating it this week. Massachusetts and Connecticut already have gay marriage, and a campaign is under way to extend it across New England by 2012.