If Pat Buchanan, the human hand grenade, lobs himself into the 2000 presidential campaign as nominee of the Reform Party, some Republicans, and perhaps some Democrats, will try to dampen his explosive force by excluding him from next year's presidential debates, as Ross Perot was excluded from the Clinton-Dole debates in 1996. Exclusion would be in the spirit of campaign finance reformers' plans to further constrict, through government regulation, political discourse.

Fortunately, Jamin Raskin, professor of law at American University, in his essay "The Debate Gerrymander" in the Texas Law Review, refutes the arguments for excluding candidates like Buchanan from the central events of presidential contests. Raskin's statutory and constitutional arguments against practices designed to disadvantage rivals of the two major parties may or may not persuade courts. However, his invocation of democratic morality should persuade fair-minded people.

In 1992, two years after winning a three-way Republican primary for lieutenant governor of Arkansas with 46 percent of the vote, Ralph Forbes ran as an independent for Congress. Although he had satisfied Arkansas's ballot access requirements, an entity of the state government, Arkansas public television, excluded him from the televised debate on the ground that he had no "serious" or "reasonable" chance to win.

It based that judgment on the opinions of "news organizations," his shortage of funds and the fact that his house was his campaign headquarters. Raskin believes, but the U.S. Supreme Court disagrees, that this exclusion -- a decision to weaken Forbes because he was weak -- violated the First Amendment by discriminating against Forbes in a public forum.

In 1996 the Commission on Presidential Debates (CPD), a private entity funded by large corporations, excluded Perot from the debates. Raskin says this action, by conferring the debates' vast television exposure on only two candidates, constituted an illegal corporate contribution to them. This issue is being litigated and is being reconsidered by the Federal Election Commission. The CPD's criteria for excluding Perot -- even though he was on all state ballots and had almost $30 million in federal campaign funds -- supposedly were "national newsworthiness and competitiveness" as judged by Washington bureau chiefs of the elite media, "prominent" political commentators, campaign managers and pollsters, "representative" political scientists at "major" universities and news coverage.

Basing exclusion on such self-fulfilling prophecies would be bad enough. But exclusion actually was a deal struck by the Dole and Clinton campaigns.

A third candidate usually hurts one of the major party candidates more than the other, and Perot particularly hurt Dole. Clinton was ahead and wanted soporific debates. George Stephanopoulos, then a Clinton aide, said after the election, "We didn't want [people] to pay attention. . . . We wanted the debates to be a nonevent."

However, even if Perot really had been excluded on "viability" or "seriousness" grounds, why should a candidate who is on 50 state ballots be excluded because some supposed experts make predictions about the voting that the debates are supposed to influence? The major party candidates for president and other offices are exempt from "viability" tests for inclusion in debates. Most congressional races are won by landslides -- candidates from one of the two major parties lose by more than 20 percentage points. Gov. Jesse Ventura was not "viable" -- until he was included in statewide televised debates with the two major parties' nominees.

Besides, says Raskin, from Robert La Follete through Perot, third-party candidates with no chance of winning nevertheless have serious purposes. Those purposes include trying to shape the nation's political conversation and articulate views of constituencies that feel neglected by the major parties.

A two-party system, although desirable, is neither endorsed nor presumed by the Constitution and should not be "sacralized" (Raskin's word) by objectionable laws and practices. Debates should be open to any candidate with a mathematical chance to win the necessary electoral votes -- any candidate who is on the ballots in states with a cumulative total of 270 electoral votes. Some people justify excluding from debates candidates not from the major parties in order to prevent "cacophony." But a high decibel level can betoken democratic vigor. Besides, if the inclusion of more than two candidates devalues presidential debates, do without debates. From Washington through Eisenhower, the nation picked presidents without face-to-face debates, and some of those presidents were not inferior to those elected since debates began in 1960.

However, debates are here to stay. And Buchanan is here. He is a good campaigner and, as a nativist and protectionist, a bad influence. He has a right to be both, without being hobbled by the major parties in collusion.