NASHVILLE, Tenn. – Barack Obama and John McCain clashed repeatedly over the causes and cures for the worst economic crisis in 80 years Tuesday night in a debate in which Republican McCain called for a sweeping $300 billion program to shield homeowners from mortgage foreclosure.

“It’s my proposal. It’s not Sen. Obama’s proposal,” McCain said at the outset of a debate he hoped could revive his fortunes in a presidential race trending toward his rival.

In one pointed confrontation on foreign policy, Obama bluntly challenged McCain’s steadiness. “This is a guy who sang bomb, bomb, bomb Iran, who called for the annihilation of North Korea – that I don’t think is an example of speaking softly.”

He spoke after McCain accused him of foolishly threatening to invade Pakistan and said, “I’m not going to telegraph my punches which is what Sen. Obama did.”

The debate was the second of three between the two major party rivals, and the only one to feature a format in which voters seated a few feet away posed questions to the candidates.

They debated on a stage at Belmont University four weeks before Election Day in a race that has lately favored Obama, both in national polls and in surveys in pivotal battleground states.

Not surprisingly, many of the questions dealt with an economy in trouble.