The top contenders to be Illinois' next U.S. senator differed sharply Monday on whether Bush-era tax cuts should be retained for the wealthy, an issue the winner will likely get to vote on within weeks after the Nov. 2 election.

Democrat Alexi Giannoulias said he backed President Barack Obama's plan to keep the tax cuts in place for the vast majority of taxpayers whose household income is less than $250,000, while Republican Mark Kirk favored extending the tax cuts across the board for two years.

Under the 2001 plan, taxes will revert to previous higher levels at the end of the year unless Congress intervenes. The issue is sure to come up in the lame-duck session of Congress, during which either Kirk or Giannoulias is likely to serve because of a court-mandated special election conducted simultaneously with the general election.

Giannoulias, now the state treasurer, said mounting deficits make it too costly to continue tax breaks for the wealthy worth hundreds of billions of dollars. "These are individuals who in many instances aren't likely to spend it (and) are likely to save it," he said. "It's not likely to spur economic growth."

But Kirk, a five-term North Shore congressman, argued that the economy is too fragile right now to add a greater tax burden for some on top of a litany of new, smaller taxes built into recently enacted laws including the health care reform package.

"I think the threat of a double-dip recession is there and we should execute policies that reduce that threat of a double-dip recession, not increase them," Kirk said.

The first joint appearance of the campaign for Kirk and Giannoulias came at a question-and-answer session with the Tribune editorial board. Also there were two other Senate contenders, Green Party candidate LeAlan Jones and Libertarian Mike Labno.

Less than a month before the election, Kirk and Giannoulias are locked in a neck-and-neck battle to take the seat once held by Obama.

The tightness of the contest served as a backdrop for a sharp divide between the candidates on a number of issues, including the Iraq war.

"Congressman Kirk didn't just vote to go into Iraq, he actually convinced other Republicans that it was necessary," Giannoulias said. "He said he knew, quote, to a moral certitude that there were weapons of mass destruction. And in one of the most important foreign policy decisions of the last quarter-century, Congressman Kirk got it wrong."

Kirk, a Navy Reserve commander, said he and others in Congress voted to green-light an invasion after being shown what turned out to be flawed evidence that Saddam Hussein had weapons of mass destruction.

"We were in the middle of the White House situation room, and we were shown, by the deputy director of Central Intelligence, tubes that they said were milled to within a millionth of an inch, not necessary for anything else but the use in" enriching uranium for nuclear weapons, Kirk said.

Kirk and Giannoulias also disagreed over immigration reform. Both said they wanted to move quickly to reinforce border security, but the Democrat said he supports simultaneously offering illegal immigrants already in this country a path to citizenship.

Kirk said border security must come before other immigration reforms are considered, including the so-called DREAM Act, which would grant conditional legal status to people who came to the country illegally as children if they attend college or join the U.S. military.

The Senate race has taken a decidedly low road with Democrats and Republicans using a barrage of TV attack ads to lob insults. Kirk has been derided as a "liar" for embellishing his military record, while Giannoulias has been called a "mob banker" for loans his failed family bank extended to felons.

Pressed to renounce such advertising, Giannoulias said he would "go positive" with ads paid for by his campaign as long as Kirk would agree to do the same.

Kirk declined. "I think we're going to have the full First Amendment in this race," he said.

Tribune reporter Jeff Coen contributed to this report.

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