WASHINGTON (AP) -- Tonight's presidential debate comes exactly four weeks before Election Day and Republican John McCain is seen as having the most riding on the meeting.

Polling suggests Democrat Barack Obama is approaching the 270 Electoral College votes needed for victory.

But McCain is said to be more comfortable than Obama in the town hall-style confrontation.

The target audience in the debate will be the roughly 10 percent of the electorate who say they're undecided, as well as the additional 25 percent who say they could change their minds between now and November 4th.

The debate is at Nashville's Belmont University, and the questions are supposed to be divided equally between the economy and foreign policy. But given the global financial turmoil and the crumbling of Wall Street, economic questions may well dominate.

The 90-minute debate will be moderated by NBC's Tom Brokaw.