(CNN) - A new national poll suggests that Sarah Palin may be hurting John McCain more than she's helping him.
A CNN/Opinion Research Corporation survey released Sunday indicates that McCain's running mate is growing less popular among voters and may be costing the Republican presidential nominee a few crucial percentage points in the race for the White House.
Fifty-seven percent of likely voters questioned in the poll say that Palin does not have the personal qualities a president should have. That's up eight points since September. Fifty-three percent say that she does not agree with them on important issues. That's also higher than in September.
"Just after the GOP convention in early September, 53 percent said they would vote for Palin over Joe Biden if there were a separate vote for vice-president. Now, Biden would beat Palin by 12 points if the running mates were chosen in a separate vote," says CNN Polling Director Keating Holland.
And what if voters were allowed to vote for president separately?
"It would be a four-point edge for Barack Obama, 52 percent to 48 percent. Since the McCain/Palin ticket is currently getting 46 percent in a match-up against the Obama/Biden ticket, it looks like Palin's presence on the GOP ballot is taking two percentage points away from McCain. In a close race, that might represent the margin of victory," adds Holland.
The poll also suggests that the overall image of the Alaska governor may be dropping in the eyes of Americans. Palin's unfavorable numbers have been growing. They are eight points higher now than in early October and are now more than twice as high as they were when McCain first introduced his running mate to the public in late August.
"John McCain has also been suspect with conservatives, the base of the Republican Party, and they were never enthusiastic about his candidacy. Palin was a unusual pick. She was well known with conservative insiders but unknown outside. When she was named there was a rush of enthusiasm among conservatives and everyone was impressed by McCain's unusual and unexpected choice. The more many Americans have found out about Palin, the less they like her," says CNN Senior Political Analyst Bill Schneider.
If McCain loses the election, should Palin run for the White House in 2012?
"Most Republicans say yes, but most Americans say no," says Holland.
Only four in ten Americans would support a Palin candidacy four years from now if McCain is not elected on Tuesday. That figure rises to 77 percent among Republicans, but even among Republicans, one in five would prefer Palin to sit out 2012.
The CNN/Opinion Research Corporation poll was conducted Thursday through Saturday, with 1,017 adult Americans, including 950 registered voters and 716 likely voters, questioned by telephone. The survey's sampling error is plus or minus 3.5 percentage points for some questions and 4.5 percentage points for other questions.