Mitt Romney, the Republican candidate for governor, acknowledged today that he filed tax returns in 1999 and 2000 saying he was a part-time resident or nonresident of Massachusetts, while he lived full time in Utah running the Winter Olympics.

The Massachusetts Constitution requires a candidate for governor to have lived in the state for seven consecutive years before running, and Mr. Romney's admission raised new questions about his candidacy. On Wednesday, he acknowledged saving $54,000 in taxes by claiming his multimillion dollar Utah house as his primary residence.

James Roosevelt, the state Democratic Party's lawyer, said at a news conference today that the party was likely to challenge Mr. Romney's residency with the state Ballot Law Commission by the deadline, 5 p.m. on Friday.

At the same time, the leading candidate for the Democratic nomination for governor, Shannon O'Brien, the state treasurer, raised a further question about Mr. Romney's residency by pointing out that in April 2000 a leading newspaper in Utah, The Deseret News in Salt Lake City, reported that Mr. Romney had declared his house in the Deer Valley section of Park City to be his primary residence