aying a ''pattern of forgery'' was evident in his nomination papers, state election officials yesterday barred US Senate hopeful Jack E. Robinson from the Republican primary ballot, dealing a major blow to his uphill bid to unseat Democratic Senator Edward M. Kennedy.
The state Ballot Law Commission, which issued the ruling, also referred the case to the attorney general's office for possible prosecution.
The commission, after two weeks of hearings, eliminated 153 signatures from Robinson's nomination papers. That left the GOP candidate 14 short of the 10,000 certified voter signatures he needed to qualify for the Sept. 19 primary ballot.
Ninety of those signatures were forged, the panel said, and were collected in four towns, a pattern panel members said Attorney General Thomas F. Reilly should examine for possible prosecution.
''Given the substantial amount of credible expert and lay testimony relating to false and fraudulent signatures, particularly in Lynnfield, Medford, Scituate, and Wakefield, it appears that criminal violations of state election laws may have occurred,'' the commission said in its 32-page decision.
Robinson was out of state traveling and not available for comment.
But his lawyer, Michael C. Gilleran, expressed strong confidence that, through an appeal to the state Supreme Judicial Court, Robinson can restore enough of the excluded signatures to qualify for the ballot.
If Robinson fails, Kennedy will be freed from facing a Republican opponent for the first time in his 38-year career in the US Senate. Six years ago, Kennedy faced his toughest reelection fight when venture capitalist Mitt Romney won the GOP nomination and used his fortune to finance his campaign.
''This is great news for Kennedy,'' said Lou DiNatale, a senior fellow at the University of Massachusetts' McCormack Center, asserting that the Republicans' problem in finding a candidate to challenge the senator is more a reflection of Kennedy's popularity than their failures.
If Robinson fails to win the GOP nomination, it will be the first time since US senators first were elected by voters directly in 1916 that the state Republican Party did not field a candidate for the office.
Gilleran said Robinson had no connection to the forgeries and attributed the matter to an overzealous signature collector who was not officially part of the Senate campaign.
''This happens all the time,'' said Gilleran. ''You always get some of these. It is hard to prevent.''
Maurice Richardson, the commission chairman and a retired district judge, said the panel had not found any evidence to conclude any particular person was responsible for the fraud.
''We are not an investigatory body,'' he told reporters after releasing the decision.
The commission's ruling is a big setback to Robinson's hopes of becoming the Republican nominee. But he has in the past vowed to fight any adverse rulings in the courts, and has said if he lost, he would mount a write-in or sticker candidacy to win a place on the November ballot.
The decision was approved 4-0 by the panel.
Yesterday, after the ruling was issued, the three staff members that Robinson hired three months ago to run his campaign quit. His press aide, Ian L. Bayne, one of those who resigned, said the departures were not necessarily related to Robinson's problems, but reflected a desire to return to their jobs working with the Republican Party on other campaigns around the state.
Robinson would need 10,000 write-in votes in the primary to win the party's nomination, a daunting task, particularly this year, when there are very few contested races. He is the only Republican running for the nomination, and there are no other statewide races this year.
In addition, Robinson, although he has personal wealth, cannot draw on the resources of the state Republican Party or Governor Paul Cellucci, who withdrew support for the campaign after embarrassing revelations about Robinson's personal life emerged shortly after he jumped into the race in March.
The most serious controversy involved a former girlfriend who took out a restraining order in 1998, alleging in a sworn statement that Robinson forced her to have sex with him. She agreed to drop the order when the two signed a court agreement.
Robinson, a 39-year-old Jamaica Plain native whose father was the longtime head of the Boston NAACP, has five days to decide whether to appeal the commission's case to court.
Robinson was defending a total of 10,139 signatures that he had submitted to Secretary of State William F. Galvin's office in early June.
But thanks to a well-financed and coordinated challenge from Democrats, the commission heard hours of testimony from subpoenaed voters who told the members that signatures of their names on the papers were fakes. The Democratic challenge also proved some of the signatures had been incorrectly certified by local election clerks, or incorrectly tabulated.
Robinson suffered a serious setback in early June when Galvin eliminated 174 signatures because they were on nomination papers that did not conform to the SJC's 1998 ruling that they had to be exact copies of official state forms. Gilleran said Robinson's best case to win a spot on the ballot is to restore those signatures eliminated by Galvin with an appeal to the SJC.
The 68-year-old Kennedy will face a Libertarian candidate, Carla Howell, in the November election. The Conservative Party, which has until August to submit 10,000 certified signatures, is also working to get a candidate on the ballot.
