With less than a week to go before the presidential election, there’s no question the 2008 race to the White House is hinging on the economy. There is a question, however, about how much power the winner will have to turn the troubled economy around.

With the nation facing its worst economic crisis in decades, economists and historians say it is hard to predict how much sway either Barack Obama or John McCain will ultimately have over the nation’s economic woes. That’s partly because the crisis is moving so rapidly and partly because a new president’s power depends in part on external factors that are difficult to gauge, such as whether he faces a cooperative Congress.

“There are limits on what a president can achieve or do, but the expectations are so great,” said Robert Dallek, a longtime presidential historian.