Keaney said he believes Zinn, the author of A People's History of the United States, will speak on the historical significance of Nader's presidential run.

Nader's Boston visit is part of an unusual campaign strategy, seeking not so much to win the election as to gain the five percent of the vote needed to qualify for federal funding in subsequent campaigns.

According to Jerome M. Mileur, who is the chair of the UMass political science department, this strategy is the most significant attribute of Nader's candidacy.

"He is, to my knowledge, the first third-party candidate for president to try to build the party within the framework of the current campaign finance laws that provide public funding for any party that gets five percent of the vote in the general election," Mileur wrote in an e-mail message.

This objective sets up a unique electoral strategy.

Both Bush and Gore are devoting few electoral resources to liberal strongholds like Massachusetts, which both candidates agree will give its electoral votes to Gore.

As a result, Nader has an open field to draw crowds and build support in areas of the country where he is already popular. These areas include liberal cities and suburbs in New England and politically independent West Coast states.

Keaney said that future rallies in Los Angeles and San Francisco may be in the works.