Birmingham went head-to-head Monday night with the tax cut's top supporter, Gov. Paul Cellucci, in the last of a series of debates between Cellucci and opponents of the tax cut.

Question 4 would cut the state's income tax from its current rate of 5.85 percent to 5 percent over three years, costing the state about $1.2 billion annually in revenues.

Cellucci says the tax cut is needed to make Massachusetts more competitive with other states -- and also to impose "fiscal discipline" on the Democratic-controlled state Legislature.

In a debate televised live on WCVB-TV, Cellucci said the money saved by the cut belongs to taxpayers, not the state government, and to reject the tax cut "would be like giving the state Legislature a blank check."

Birmingham acknowledged having a tough argument to make. He conceded the money belonged to taxpayers, but said there are essential taxpayer services that could use it.

"It's your money. No one's arguing that," Birmingham said. "But it's also your roads, your bridges, your parks and your schools."

The ballot question would also force lawmakers to make good on a promise to return the rate to 5 percent after twice raising it during the fiscal crises of the late 1980s and early 1990s, Cellucci said.

But opponents, such as Birmingham, say chopping the income tax rate so drastically is a risky fiscal proposition for the state, especially if voters also approve Question 6 that would create tax credits for tolls and excise taxes.

Combined, the two questions could result in a $2 billion annual cut in state revenues. Cellucci opposes Question 6.

Birmingham has denied there was a promise made to roll back the tax.

Two recent voter surveys suggest Birmingham and other opponents have their work cut out for them.

A poll published in Monday's edition of The Boston Globe reports that 56 percent of voters support Question 4 and only 26 oppose the measure. A poll by the Boston Herald last week found a narrower margin -- about 48 to 30 percent in favor of the question.

Both polls surveyed about 400 likely voters in Massachusetts.

The debate with Birmingham is the last of four tax cut debates between Cellucci and Democratic opponents, each of whom is said to be weighing a run for governor -- including House Speaker Thomas Finneran, state Treasurer Shannon O'Brien and former Democratic National Committee Steve Grossman.

Of the four, Grossman and Birmingham have been running hardest. Grossman has already publicly said he is a candidate.

On Monday, Birmingham reported more than $1.9 million in his campaign committee account, well ahead of other potential candidates, such as Finneran, who reported about $399,000.