Running even just 20 days before the election, President Bush (search) and Sen. John Kerry (search) are looking for any edge in their third and final debate Wednesday night.

The face-to-face meeting, scheduled for 9 p.m. EDT at Arizona State University, is limited to economic and domestic policy, but there may be questions that allow Bush to discuss foreign policy, the war in Iraq and his campaign against terrorism — all issues the Republican's campaign thinks he does well on.

"There could be times when those issues come up," said Bust, concern over Social Security (search) reserves and increasing Medicare premiums.

Kerry's campaign is publicly showing a lot of confidence in his performance. Lockhart said Kerry won the first two debates and that campaign advisers "cannot remember an incumbent who lost three consecutive debates in the mind of the public who then went on to victory."

Despite their public assurances and the fact that Kerry has spent most of the campaign until recent weeks attacking Bush's domestic record, the senator spent two days secluded in a New Mexico hotel trying to master the debate material.

For Bush, Wednesday's debate is a chance to revive in public opinion polls as the clock ticks down to Election Day, Nov. 2. His job-approval rating slumped to 47 percent in a USA Today-CNN-Gallup poll published Tuesday — one point above the lowest point in his presidency, reached in May.

As in the first debate, the candidates take questions standing at lecterns. Bob Schieffer of CBS News will moderate.

At a rally Tuesday in Colorado Springs, Colo., Bush mocked Kerry's credibility and said the debates so far "have highlighted the clear differences between the senator and me on issues ranging from jobs to taxes to health care to the war on terror."

Bush said Kerry would have to raise taxes to pay for all of his proposals. Kerry says he would pay for them by repealing Bush's "unaffordable" tax cuts for people making more than $200,000 and scaling back other government spending. He promised during the second debate that he would not raise taxes for those who make less.

"The problem is," Bush said Tuesday, "to keep that promise, he would have to break almost all of his other ones. ... To pay for all the big spending programs he's outlined during his campaign, he will have to raise your taxes. He can run from his record, but he cannot hide."