"It's already bee decided that whether or not you have a ticket you are not welcome in the debate," John Bezeris, a representative of the sponsoring Commission on Presidential Debates told Nader. The commission's criteria excluded all but Democrat Al Gore and Republican George W. Bush.

"I didn't expect they would be so crude and so stupid," Nader said afterward. "This is the kind of creeping tyranny that has turned away so many voters from the electoral process."

Nader had received the ticket as a gift from Tod Tavares, a 21-year-old Northeastern University student who said he got it from a roommate.

Bezeris, who was surrounded by several police officers at the debate site at the University of Massachusetts-Boston, told Nader he could not enter because he was not an invited guest.

Nader was among a trio of third-party presidential candidates who did their best Tuesday to keep the Republican and Democratic nominees from hogging the show.

Hours before the debate, a judge threw out a court challenge filed earlier in the day by Massachusetts Libertarians to try to force organizers to include their candidate, Harry Browne.

"The plaintiffs have slept on their rights by waiting until the last minute to seek relief," Suffolk Superior Court Judge Gordon Doerfer ruled. He said intervening in the debates would deprive the public of information it needs about the candidates.

The lawsuit claimed Browne should be included because Massachusetts, which officially recognizes the party, spent $900,000 to help pay for the debate.

Earlier, Nader criticized the commission's decision to limit the debate to candidates with more than 15 percent support in national polls; only Bush and Gore qualified.

"They have the keys. This debate commission is a private company created by the two parties," Nader told about 1,000 supporters. "The thing is why do we as a society let them control the gateway? Why don't we have many gateways, many debates?"

As he concluded his remarks some students chanted "Let Ralph debate! Let Ralph debate!"

Reform Party candidate Pat Buchanan, meeting reporters in his Boston hotel, said it was unfair to keep his party out.

"I feel like Slippery Rock State Teachers and we made the Final Four of the NCAAs and they won't even let us in the gymnasium," Buchanan said. "They won't even let us on the gym floor to show what we can do."

Buchanan, who has more than $12 million in federal campaign funds to spend, outlined plans to launch an advertising campaign next week in states he says have been abandoned by Republicans, including California, New Jersey and most of New England.

He is aiming for 5 percent of the popular vote in the Nov. 7 election to guarantee that the Reform Party gets federal matching funds again in 2004. Buchanan said the ads would run mainly on Christian radio stations and would highlight local concerns, such as immigration in California and Arizona.