Inside the UMass-Boston hall, Tuesday’s presidential debate went well for both Vice President Al Gore and Gov. George W. Bush. They effectively restated their positions, they made no dreadful mistakes, they gave supporters reason to continue that support, and perhaps the undecideds reason to begin leaning. Though unspectacular, it was informative and enlightening.

The scene outside offered more spectacle, in an unsettling and unfortunate way. Several thousand protesters demonstrated against the exclusion of all but the two major party candidates; Green Party nominee Ralph Nader was denied entry to the hall despite having a ticket.

Mr. Nader and Reform Party candidate Pat Buchanan should be included in these debates. The Green Party is an established organization in every state. The case for the Reform Party is even stronger – it has drawn more than enough votes in the last two presidential elections to qualify for federal campaign funds.

The reason two of the four credible candidates are being factored out is a classic example of circular reasoning. The Commission on Presidential Debates says the admission criteria are set by its nonpartisan board and the specific rules developed through consultation with campaigns that meet those criteria. The nonpartisan board, however, is strictly bipartisan; its members are exclusively Republican and Democratic leaders, making the claim of party blindness insupportable. The claim by the campaigns that they are powerless to affect participation guidelines is, given their sway over everything from the debate formats to the size and shape of the podiums, simply absurd.

Third, and even fourth, party candidates could be included if the will was there to do so. The nonprofit commission was established in 1987 to ensure that debates would be a permanent part of every presidential election. Given the growing interest during the last 13 years in alternative parties, logic would dictate that the commission would adopt rules to accommodate this very real change in the political climate.

Instead, the commission tightens the rules. The extent to which a party is organized and active once was the decisive factor in whether that party’s candidate would have the opportunity to convey that party’s message in the most prestigious and visible of forums. Now, candidates must demonstrate at least 15-percent support in five selected polls. In other words, for a third party to be able to convey its message in the debates, it first must convey its message to a substantial degree in some other forum, such as through advertising campaigns third parties cannot afford.

The larger question of affordability is whether the nation can afford the suspicion and disgruntlement that results from the intentional exclusion of all but the two major parties. Mr. Nader notes that inclusion of upstart parties can have profound effect – Jesse Ventura was polling in single digits just weeks before Minnesota’s 1998 gubernatorial election; his performance in a debate propelled the Reform candidate to victory. Mr. Nader also notes that the commission’s emphasis on polls with its 15 percent standard conflicts with its refusal to recognize the numerous polls that show more than 60 percent of Americans would like to see him and Mr. Buchanan in at least one of the debates.

The Ventura case was an exception; it is most unlikely either Mr. Nader or Mr. Buchanan would move voters to such an extent. It is possible, however, that one or the other could move enough voters to severely damage one or the other major party candidates. It happened in 1992 with the candidacy of Ross Perot.

Excluding credible candidates from the debates is one way to prevent that from happening again. It’s just not the right way. There are four established national parties in this election; a debate between only two is half a debate. But the debate season is only one-third completed; the remaining debates on Oct. 11 at Wake Forest University and on Oct. 17 at Washington University in St. Louis provide opportunity for the commission and the major parties to correct this faulty equation.