The Commission on Presidential Debates, anticipating another firestorm about its entry standards, is wrestling with a possible rewrite of its rules for deciding which third-party or independent candidates to invite into next autumn's televised debates.

The nonprofit group, which included Ross Perot as an independent in 1992 but barred him as the Reform Party nominee in 1996, hopes to announce its standards for admission to the 2000 debate very early next year, commission executive director Janet Brown said yesterday.

With Patrick J. Buchanan declaring yesterday that a principal motive for his leaving the GOP and joining the Reform Party is his hope of participating in the presidential debates, the commission is well aware that it may be under the gun again.

Even as its review is underway, the Federal Election Commission is weighing a petition from Reform Party members in Virginia to preempt the private group and require that televised debates include any presidential candidate who has spent at least $500,000 on the campaign and is on enough state ballots to have a mathematical chance of being elected. FEC Chairman Scott Thomas said in an interview he favors a review of the debate commission criteria, but is not certain of enough support from other commissioners to predict whether the FEC will act.

The debate commission was formed in 1987 by leaders of the Republican and Democratic parties and has sponsored the general election debates in the last three election cycles.

A formal complaint brought by Perot's attorneys in 1996 was dismissed by the FEC--an action Perot's lawyers said was a reflection of "bias" on the part of the commissioners, all of whom are Democratic or GOP appointees. Perot supporters have made the same contention about the debate commission itself, which has been headed throughout its existence by Frank J. Fahrenkopf Jr. and Paul G. Kirk Jr., the former chairmen of the Republican and Democratic national committees, respectively.

Fahrenkopf, Kirk and Brown, the executive director, all pointed out that the commission has consistently used the same set of 11 standards devised by an advisory group headed by Richard Neustadt, an authority on the presidency and emeritus professor at Harvard. The commission unanimously supported Neustadt's recommendation that Perot be included in his first race and excluded in the second. The current criteria are supposed to provide objective measurements of a candidate's realistic chances of being elected.

Neustadt said in an interview that in 1992 Perot was self-financing his race, which meant he had potentially unlimited funds, and polls and news coverage indicated he had a chance of winning enough electoral votes to deny President George Bush and challenger Bill Clinton an electoral college majority--thus forcing the contest into the House, where members would choose from among the top three contenders.

In 1996, Perot accepted public financing, which limited his spending, and the indicators from polls and news coverage were that he would receive far less than the 18 percent he won in 1992. And, as Neustadt said, "in 1996 we knew that even with 18 percent of the popular vote, he failed to carry a state or win a single electoral vote."

But all the commission officials said they were reevaluating the admission standards. "We do that every cycle," Fahrenkopf said. "We have won every legal fight, but we haven't really established the credibility we thought we had with the American people and the media. We hope this time we can write clear criteria early enough so everybody understands why we invite certain people and not others."

Perot's supporters contend that his exclusion in 1996 denied him a fair chance to compete, and they point to the explosion of support for Reform Party candidate Jesse Ventura after he was invited into the 1998 Minnesota gubernatorial debates as evidence that early polls are not a reliable indicator of potential support.

But Brown said the commission believes the debates "are not a ticket of admission to the race," but rather, an aid to voters in "making their final decision on who should be president of the United States."

Kirk said that--and not "popular entertainment"--was the goal, but conceded that "I'm troubled" by the fact that the major parties will be choosing their nominees so early in the election year and "their nominating process has become more and more a function of money." Excluding other contenders under these circumstances, he said, "could further disillusion people with the whole process."

Neustadt said that criticism has persuaded him "we'd be justified in making the criteria simpler and more automatic. Our reliance on the electoral college arithmetic is something neither the media nor the public understood. It has left the commission trying to explain the inexplicable."

But Neustadt cautioned that "if new criteria make it easier for more than two candidates to get into the debates, the major-party nominees may just refuse to participate, and then you've lost your best tool for informing the public. But there's a terrible hazard in public credibility if we keep doing the same thing."

CAPTION: A supporter of Reform Party nominee Ross Perot protests his exclusion in October 1996 from the second debate between President Clinton and Republican nominee Robert J. Dole at the University of San Diego. Perot participated in the 1992 debates as an independent.