Former Sen. Paul Tsongas officially announced Tuesday that he is a candidate for the Democratic presidential nomination, confronted with the question that will almost certainly hound him throughout his campaign.

"How are you going to deal with being another liberal Greek from Massachusetts?" he was asked by a skeptical Boston reporter, referring to the disastrous legacy of Michael S. Dukakis' failed 1988 presidential campaign."Well," Tsongas deadpanned, "I applied to be Norwegian, but. . . ."

The incident partially defines the difference between Tsongas, who left the Senate in 1984 to successfully battle cancer, and Dukakis, a man who was at best uncomfortable with humor, especially the self-deprecating sort.

Tsongas is the first person of either party to officially announce his candidacy. Former South Dakota Sen. George McGovern, who suffered one of the worst defeats in U.S. political history when he lost in 1972 to President Richard Nixon, has said he is considering seeking the Democratic nomination but has not announced.

Tsongas, 50, who formally announced his presidential campaign in his hometown of Lowell before heading off to Manchester, N.H., to begin his campaign, is adroit at using a quick one-liner to disarm critics or to drive home a point.

During an address to students in Durham, N.H., last month, Tsongas took aim at the Republicans, who he said, believe "the free market will take care of everything."

"You know where they applaud loudest?" he asked. "Tokyo."