John J. Ford, a U.F.O. enthusiast accused of masterminding a plot to assassinate three political officials in Suffolk County, was found unfit to stand trial today. A judge ordered that he be sent to an upstate psychiatric institution for at least a year.

Mr. Ford, 48, was arrested a year ago on charges that he was scheming to kill John Powell, the chairman of the Suffolk County Republican Committee; Fred Towle, a Suffolk legislator, and Anthony Gazzola, a leader of the Conservative Party in Brookhaven and chief investigator in the Brookhaven Town Attorney's office, by putting radium in their cars and lacing their toothpaste with radioactive metal.

Investigators said Mr. Ford wanted the three officials killed because he believed they were interfering with his efforts to contact aliens from outer space. Mr. Ford's friends said he believed that visitors from outer space had crash-landed on Long Island and that government officials were keeping the aliens at Brookhaven National Laboratory in Upton and that they had created diversionary fires in Long Island's Pine Barrens to conceal the aliens' crash landings.

After reviewing reports from several psychiatrists, Judge Anthony Corso of Suffolk County Court concluded that Mr. Ford was delusional and sent him to the Mid-Hudson Psychiatric Center in New Hampton, N.Y. The Suffolk County District Attorney's office withdrew its motions contesting the results of the psychiatric tests.