The union that brought New York City transit to a screeching halt for three days last month voted down a new contract Friday.

The workers rejected the contract by a seven-vote margin out of more than 22,000 votes cast. The vote is a big blow to TWU President Roger Toussaint, who helped trigger the mass walkout and campaigned heavily for a yes vote.

The agreement would have provided workers with raises of 3 percent, 4 percent and 3.5 percent over the next three years. But it would have required them for the first time to contribute 1.5 percent of their salaries toward health care premiums.