Candidates prepare for second debate

By John Whitesides, Political Correspondent

NASHVILLE (Reuters) - Republican John McCain hopes to halt Democrat Barack Obama's momentum and gain new life in the White House race 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 turning 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. British time on Wednesday).

Obama has solidified his national lead 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, but other polls have shown a bigger margin for Obama.

The economic turmoil continued on Monday, when stocks tumbled on Wall Street in a sign the $700 billion (397 nillion pound) government bailout of U.S. financial concerns did not ease market concerns about the economy.

McCain'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.  Continued...