While Democrats made virtually a clean sweep of the partisan races in Massachusetts yesterday, party leaders were handed a significant defeat when voters approved a ballot question that significantly cut the state's income taxes.

Voters also handed a surprising defeat to the backers of Question 5, which would have took steps toward a universal health care system in Massachusetts. Polls as late as this past weekend had shown the question with over a 20 point lead.

Democratic leaders had urged a vote against Question 4, which will reduce the income tax rate from its current 5.95 percent to 5 percent over the next three years.

Realizing the difficulties associated with defeating a proposal that gives money back to voters, Democrats tried to make the vote a referendum on Gov. A. Paul Cellucci and Lt. Gov. Jane Swift. Polls show both have low popularity in the state.

With 77 percent of precincts reporting as of 1 a.m., Question 4 received the support of 60 percent of voters.

Surprisingly, according to exit polling conducted by Voter News Service, the tax cut plan had significant support among those describing themselves as liberals, despite the Democratic Party's opposition. Four of 10 liberal voters cast "yes" votes on Question 4.

Democrats had argued that the cut would make it difficult for the state to address key issues, such as education and health care. They also had argued the cut was irresponsible given the chance of an economic downturn.

Republicans, in a ultimately successful argument, told voters the state could afford the cuts, given the current surpluses the state was running. They also argued such cuts had been promised by the legislature in the early 1990s.