In the final televised debate of the campaign, Gov. Deval Patrick and Republican Charles Baker went toe-to-toe last night over the economy, immigration and Baker's role in the Big Dig financing plan as the four candidates for governor polished their pitch to voters a week before election day.

The debate - moderated by former ABC World News anchor Charles Gibson - focused heavily on the economy and each candidate's plan to put people back to work, but sparked several heated exchanges between the two front-running candidates over taxes and the Big Dig.

Baker defended a newly revealed memo he wrote in 1998 warning that Big Dig spending threatened to force "Draconian" cuts to other public transportation projects, an apparent contradiction to other public statements Baker made at the time regarding to Big Dig spending.

"The memo that I wrote was about my concern about state spending overall and the growth in spending on the state side which had been growing at a significant rate," Baker. "We were continuing to grow the level of spending that we were seeing on the statewide side at the same time we had a fixed set of expenses associated with the Dig."

The memo written by Baker while serving as budget chief for then-Gov. Paul Cellucci expressed concern that rising Big Dig costs were "simply amazing" and that state officials would at some point have to take "Draconian measures to deal with the transportation spending plan."

Baker, in the leaked memo first reported Sunday by the Associated Press, proposed a series of steps that could be taken to address the problem - including a $300 million draw from reserved - but suggested those steps be delayed until after the election.

When pressed by Gibson to square what he wrote with public comments made to the Legislature insisting he could "not see how anybody could argue that the Artery will be pulling money away from non-artery projects," Baker said it was not a contradiction.

"It was exactly the kind of memo, frankly, we should see out there," Baker said, steering the conversation to Patrick by raising the specter of a projected $2 billion shortfall in next year's fiscal budget. "I certainly hope someone is writing a memo you that's telling you how were going to get out of that one," Baker said, addressing Gov. Deval Patrick.

Patrick turned the focus back on the Big Dig, accusing Baker of sticking the memo in his pocket instead of alerting the public to his concerns.

"We all knew the Big Dig financing plan was flawed from the start. It turns out Charlie knew it was flawed from the start, and for political reasons didn't make that public," Patrick said. "So I can tell you I am very reluctant to take fiscal advice from the architect of the Big Dig financing plan."

Treasurer Tim Cahill, an independent who is trailing both Baker and Patrick by wide margins in the polls, said that "the biggest think that bothered me about the memo is that it was going to be hidden until after the election of Gov. Cellucci."

The hour-long debate, sponsored by a Boston media consortium including WHDH, NECN, WBUR, WGBH, and the Boston Globe, featured the candidates seated at a round table with no time limits for responses, resulting in a free-flowing discussion between the candidates.

Challenged by Gibson to explain the job losses and a near doubling of the unemployment rate on his watch, Patrick blamed the "global economic collapse."

"I don't think any one of us could have prevented that," he said. "I'm not declaring victory by any means, but we're making progress and no one is working harder to get out of this than I am."

Baker and Patrick have been quarreling for almost a week over the latest jobs report in Massachusetts that showed a sharp drop in unemployment from 8.8 percent to 8.4 percent, but also showed a loss of 21,000 jobs.

"For me this whole thing is you have to be real about what's really going on out there," Baker said, claiming he is the only candidate to put forward concrete plans to reform state government that will save money. He called those reforms "difficult, disruptive and tough but they are specific and are far more than the treasurer or the governor have put out there to solve this problem."

Asked how he would enact those reforms given the fact that the Legislature has already rejected many similar proposals, Baker said, "I'm going to lead on some of those issues. I'm going to take the ball and run with it."

He said lower taxes and a more consistent regulatory policy are necessary to instill confidence in businesses and make Massachusetts a more competitive state to grow jobs.

Cahill painted himself as the only candidate who came from the middle class and new what it meant to grow a business and jobs from the ground up.

"I know the governor said he sees the faces of people behind the budget cuts, but I don't think he sees the faces of the middle class when he raised taxes," Cahill said.

Patrick contended that he closed $13 billion worth of budget gaps over four years because of the economic meltdown, cutting four-times the amount of spending that was raised through new taxes.

All four candidates reiterated opposition to a ballot question to lower the sales tax to 3 percent, Patrick said it would lead to a "calamity." He then went directly at Baker, insisting that the Republican's plan to lower the sales, income and corporate taxes to 5 percent would have "exactly the same impact."

Baker said he believed lower taxes would lead to job growth, suggesting that second-term for Patrick would inevitably lead to more tax increases.

"The governor's only proposal, from what I can tell, to deal with the current $2 billion problem, is going to be to raise taxes," Baker said.

Patrick responded forcefully: "You've never heard that proposal from me. You've been saying that for 15 months and you've never heard that from me. Never."

Stein portrayed herself as the only true outsider in the race, repeating her criticism that government is wasting money on tax giveaways to big corporations like Raytheon, Fidelity and the film industry while cutting local and programs for seniors.

Asked by Gibson whether they would feel responsible at the end of the campaign for costing either Patrick or Baker the election, Cahill and Stein offered justifications for remaining in the race.

"Real politics is giving people the choices. Jefferson came about from a split vote. I believe that's what our founding fathers were looking at," Cahill said, lamenting the millions spent by "Washington outsiders" trying to tell Bay State residents how to vote.

Stein said her presence in the campaign forced the candidates to discuss issues that might have been ignored. Patrick and Baker expressed admiration for Cahill and Stein and supported their right to run and participate.

As the conversation shifted to immigration, Patrick and Stein said they opposed an Arizona-style law in Massachusetts because they worried it would create a "climate of fear" in legal immigrant communities and erect a wall between those residents and local law enforcement.

Cahill said he supported giving police the "tools they need" to take illegal immigrants off the streets.

Baker said the Arizona law may be "more than we need" in Massachusetts, but whacked Patrick for reversing former Gov. Mitt Romney's policy that create a special state police unit tasked with working with federal immigration officials to detain illegal immigrants.

In a moment of levity, the candidates were asked to name a favorite movie star. Cahill picked Jack Nicholson, Patrick picked Halle Berry, Baker picked movies by Pixar and Stein said she couldn't name any in particular.