McCain and Democratic opponent Barack Obama both backed the unprecedented rescue package that was designed to avert a meltdown in the U.S. financial system and a deep recession, threats that have compounded already heavy voter anxiety. The wobbling American economy was intruding as deeply on this presidential contest as any since the 1930s Great Depression.

After last week's first presidential debate — about half of which was devoted to the economy — a Quinnipiac University survey showed Obama's support had jumped to 50 percent or above in the key states of Florida, Ohio and Pennsylvania. Since 1960, no president has been elected without winning two of those three states.

A CNN/Time/Opinion Research Corp. poll showed Obama leading in the battleground states of Florida, Minnesota, Missouri, Virginia, and Nevada, though in some cases the difference was as narrow as 1 percentage point.

Nationally, The Associated Press and GfK, Obama surged to a seven-point lead, 48-41 percent, according to an Associated Press-GfK poll.

Senate approval of the Bush administration rescue package reversed the plan's fortunes three days after its stunning rejection in the House of Representatives. That vote produced a 778-point stock market nose-dive — the largest one-day point drop in history.

Since its rejection in the House, the bailout package — backed in its final form by both McCain and Obama — was juiced up with a number of tax breaks and other "sweeteners" designed not only to capture a Senate majority Wednesday night but also to overcome conservative objections when it is called back to the House floor later this week.

Sandwiched between those votes is Thursday's much-anticipated debate between Democratic Sen. Joe Biden, Obama's vice presidential running mate, and Alaska Gov. Sarah Palin, McCain's pick as No. 2, capping one of the most tumultuous two weeks of any presidential race in recent memory.

Before the Wednesday night Senate vote, Obama took the floor to warn that rejection of the plan risked wreckage of the American financial system.

"This will not solve all our problems," Obama said. "This is what we need to do right now, to prevent the possibility of a crisis turning into a catastrophe."