Republican Mel Martinez (search), hoping to become the first Cuban-American senator, criticized his opponent Monday for saying she would not have voted for the war in Iraq "knowing what I know now." The first debate between Martinez and Democrat Betty Castor (search) comes as a new poll found Castor had erased the small gap between them.

The two are tied among voters in the race to succeed retiring Democratic Sen. Bob Graham (search), according to a poll released Monday. Each was the choice of 45 percent of respondents, according to the Mason-Dixon Polling & Research survey. Nine percent were undecided in the race that could set the balance in the Senate.

On Monday, in the first of two debates, the candidates presented stark differences on President Bush's tax cuts, a proposal to increase minimum wage, how to solve a looming crisis in the Social Security program, and the decision to go to war against Iraq.

"It was the right decision," Martinez said. "Whether or not Saddam Hussein had weapons of mass destruction. He certainly had the intent and had been supporting terrorists."

Castor said that now that the United States is in Iraq, it has to finish the job, but said it also has to repair relations with other nations.

"We have got to continue to fight to get back that high ground and that respect among other nations," said Castor, a Democratic former state education commissioner.

Martinez, who was encouraged by the White House and Republican Senate leaders to resign as Bush's housing secretary to run for the seat, backed the president's proposal to let people invest Social Security taxes in the stock market. Castor says the proposal is too risky.

"There is no imminent danger, there is no immediate problem to Social Security," Castor said, adding that it will take "decades" for problems to surface.

Martinez said he supports allowing younger people to invest their Social Security taxes.

"Why would they not have an opportunity to invest in a private account that would permit them an opportunity to also receive a larger return than the 2 percent Social Security provides?" he asked.

Martinez also defended Bush's tax cuts, saying they "created economic opportunity, which created growth, which put people back to work."

Moderator Tim Russert of "Meet the Press" opened the debate with a question about Sami Al-Arian, who was a professor at the University of South Florida when Castor served as the school's president. Al-Arian, who is awaiting trial on charges he helped raise money for terrorists, has become a focus of recent campaign ads from both candidates.

Martinez has said Castor did not do enough to remove him from the university's staff, while Castor says she was the only person to take action against him at the time. Al-Arian was not mentioned during the debate.

But Russert, citing e-mails and calls from Floridians, asked the candidates if they would agree to halt ads focusing on Al-Arian.

Castor said she would remove her ads, but would not "do anything unless I have a pledge from Mr. Martinez that he would remove these despicable ads."

Martinez said he would not "make the strategy for my campaign here tonight under these lights."