BOSTON -- Secretary of State Michael J. Connolly has reversed his December decision to exclude former Ku Klux Klansman David Duke from the Massachusetts Republican presidential primary ballot.

Mr. Connolly said that the threat of a lawsuit from the American Civil Liberties Union left him no choice but to award Mr. Duke a ballot spot.

"As much as I find this distasteful . . . given the legal maneuverings that have gone on, he will have a place on the ballot," Mr. Connolly said Friday.

Marc Ellis, a spokesman for Mr. Duke's campaign, said that as a result, Mr. Duke would come to Massachusetts in February to campaign.

Mr. Connolly said the ACLU had informed him that it would file suit tomorrow if he held to his decision to keep Mr. Duke off the ballot.

Mr. Duke, who has had ties to both the KKK and to neo-Nazis, is considered a pariah by national Republican Party leaders. As the Republican candidate, he lost in November to a Democratic opponent in the Louisiana gubernatorial race.

He has since declared that he will challenge President Bush in some GOP presidential primaries.

Massachusetts law directs the secretary of state to place on the primary ballot those who are recognized nationally in the media as serious candidates.