Ford had said he would make an announcement after the weekend. Sources told Eyewitness News reporter Dave Evans that he decided not to run.
Ford wrote in a New York Times op-ed piece published Monday on the newspaper's Web site that if he were to run "the likely result would be a brutal and highly negative Democratic primary."
Ford has spent the past seven weeks gauging support for a possible Democratic primary challenge to Gillibrand, who was appointed to the seat by New York's governor when Hillary Rodham Clinton became U.S. secretary of state.