"Bush has now tied Richard Nixon's worst rating ever, taken in a poll just before he resigned in 1975, and is only 2 points higher than the worst presidential approval rating in history, Harry Truman's 22 percent mark in February 1952," says CNN Polling Director Keating Holland.

And that's bad news for McCain, because the poll suggests a growing number of Americans believe the Republican presidential nominee would have the same policies as the current Republican president. Fifty-six percent say McCain's policies would be the same as Bush, up from 50 percent a month ago.

The financial crisis also appears to be contributing to Obama's increased lead in the poll. Sixty-eight percent are confident in the Democratic presidential nominee's ability to handle the financial crisis, 18 points ahead of McCain, and 42 points ahead of President Bush.

More Americans appear to have an unfavorable view of Gov. Sarah Palin, and that may also be helping Obama in the fight for the presidency. Forty percent now have an unfavorable view of Palin, up from 27 percent a month ago and from 21 percent in late August, when McCain surprised many people by picking the first-term Alaska governor as his running mate.