McCain aims to stop Obama momentum in debate

By John Whitesides, Political Correspondent

NASHVILLE, Tennessee (Reuters) - Republican John McCain hopes to halt Democrat Barack Obama's momentum and gain new life in the White House race with a strong performance on Tuesday when the presidential rivals meet in their second debate.

With four weeks until the November 4 election, the debate offers McCain one of his last chances to recast a presidential race that has been shifting towards Obama in the last few weeks.

"McCain has a big opportunity with this debate," said Peter Brown, assistant director of the Quinnipiac University poll. "He has to change the dynamic and make people re-evaluate Obama."

The debate at Belmont University in Nashville, Tennessee, will begin at 9 p.m. EDT ( 2 a.m. Wednesday British time).

Obama has solidified his national lead in polls and gained an edge in crucial battleground states as the Wall Street crisis has focussed attention on the economy, an area where polls show voters prefer the Illinois senator's leadership.

A Reuters/C-SPAN/Zogby poll released on Tuesday gave Obama a 3-point edge on McCain, 48 percent to 45 percent, and other polls have shown a bigger margin for Obama.

The economic turmoil continued on Tuesday, with stocks tumbling for the second consecutive day in a sign the $700 billion (401 billion pound) bailout of U.S. financial institutions did not ease market concerns about the economy.

The Arizona senator's campaign has unleashed a volley of attacks on Obama in the last few days as his advisers signalled they wanted to turn the debate away from the economy.