Apparently convinced his list of enemies isn't long enough already, Nixon speechwriter and campaign strategist Patrick J. Buchanan took on the Institute of Politics this week.

Under questioning by Senators Herman Talmadge (D-Ga.) and Edward Gurney (R-Fla.) of the Senate's Watergate committee, Buchanan defended his recommendation that the tax-exempt status of nonprofit foundations be reexamined and if possible made a subject of public debate by advancing the theory that most if not all such foundations--specifically the Ford Foundation, the Brookings Institute and the Institute of Politics--belong to what he called America's "liberal establishment."

These and other institutions have overlapping boards of directors, Buchanan said, and they generally fund liberal projects and reach liberal conclusions, lending such conclusions publicity and plausibility they really don't deserve.

"We try to be as balanced as we can," Ernest R. May, professor of History and director of the Institute, said Thursday, without completely disputing Buchanan's thesis.

"It sounds like part of the Republican conspiracy theory," said Jeffrey Sagansky '74, chairman of the Institute's Student Advisory Committee and a Young Republican. "If there is a bias, it's just because of the rather myopic liberal bias of academe in general."

Yesterday Doris H. Kearns, assistant professor of Government and assistant director of the Institute, joined in, with similarly mild criticism of Buchanan.

"It's interesting to have a conservative make the same critique of the interlocking left-liberal directors that radicals have for years," she said. "I don't say he's totally wrong, I just don't think it's such a problem."