(CNN) -- With just four weeks left until Election Day, Sens. Barack Obama and John McCain are preparing to face off in Tuesday night's high-stakes presidential debate.
Sens. John McCain and Barack Obama will meet again Tuesday in Nashville, Tennessee.
The debate comes amid stepped-up attacks from both nominees' camps.
Gov. Sarah Palin, McCain's running mate, accused Obama of "palling around with terrorists who would target their own country," and Obama's campaign released an ad quoting editorials that called McCain "erratic" and "out of touch."
On Monday, the Obama campaign released an online documentary criticizing McCain over his involvement in the Keating Five scandal of the 1980s.
The back-and-forth this weekend could set the stage for a more heated event than the first presidential debate, one that had few sharp exchanges as both candidates largely stuck to their talking points.
McCain "has signaled to his supporters that he is going to be very aggressive in this debate," Obama campaign spokesman David Axelrod said en route from Asheville, North Carolina, to Nashville, Tennessee, on Tuesday.
"He is going to take the gloves off. So I hope in the course of it, he has time to speak to the state of our economy, which is in deep trouble right now."
Axelrod said Obama is "prepared for a very aggressive debate."
At a campaign event in Denver, Colorado, last week, a voter asked McCain when he was going to "let the gloves come off and go after" Obama.
McCain's response: "How about Tuesday night?"
According to CNN's latest poll of polls, Obama leads McCain by 6 percentage points, 49 percent to 43 percent.
The poll of polls consists of three national surveys: Marist (September 28-30), Gallup (October 2-4) and Diageo/Hotline (October 2-4). It does not have a sampling error.
As the economic crisis unfolded over the past month, Obama has reclaimed and solidified his lead.
The first presidential debate was supposed to be about foreign policy, but much of it focused on the economy.
That debate, which took place September 26, came as talks over the government's bailout proposal imploded.
It wasn't clear whether the first debate would even take place, because McCain suspended his campaign, he said, to focus on the financial crisis. By the morning of the debate, he said he thought Congress had made enough progress on the bailout proposal for him to go ahead with the debate. Democrats blasted his move as a political stunt.
A national poll of people who watched the first presidential debate suggested that Obama came out on top, but there was overwhelming agreement that both Obama and McCain would be able to handle the job of president.
Tuesday's debate is the second in the series of three presidential debates, but the format is different than the other two events.
The second debate, taking place in Belmont University in Nashville, will be set up like a town hall meeting.
The first and third debates are divided into approximately eight 10-minute segments. The moderator introduces each segment with an issue and gives each candidate two minutes to respond. Then there is a five-minute discussion period, when direct exchanges between the candidates occur.
The candidates will not only take questions from moderator Tom Brokaw of NBC News on Tuesday; they'll also answer questions from the audience and from Internet participants.
The audience will be made up of uncommitted voters.
"These debates, town hall debates, are often very telling. They often provide the most dramatic moments in a campaign," said Bill Schneider, CNN's senior political analyst.
"If either of the candidates tries to go negative when you're with an audience of ordinary voters, they don't like it. We've heard them sometimes get very upset when the candidates start attacking each other, so that's going to be hard to do in a town hall format," he said.
At the beginning of the campaign season, McCain invited Obama to participate in joint town hall meetings, but the campaigns never reached agreement on details of the proposed meetings.
McCain spent time at his ranch near Sedona, Arizona, this weekend to prepare for Tuesday's debate. Obama spent time preparing with his staff at a resort in Asheville, North Carolina, on Sunday, taking a break for an afternoon rally.