WASHINGTON (CNN) -- A new national poll suggests Sarah Palin may be hurting Republican presidential nominee John McCain more than she's helping him.

A CNN/Opinion Research Corporation survey released Sunday indicates McCain's running mate is growing less popular among voters and may be costing him a few crucial percentage points in the race for the White House.

Fifty-seven percent of likely voters questioned in the poll said Palin does not have the personal qualities a president should have. That's up 8 points since September.

Fifty-three percent say she does not agree with them on important issues. That's also higher than 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," said CNN Polling Director Keating Holland.

And what if voters were allowed to vote for president separately?

"It would be a 4-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 2 percentage points away from McCain. In a close race, that might represent the margin of victory," Holland said.

The unfavorable numbers for Palin, Alaska's governor, also have been growing. They are 8 points higher in the current poll than in early October, and they're twice as high as they were when McCain announced his running mate in late August. iReport.com: Share your thoughts on Palin

"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," said Bill Schneider, CNN's senior political analyst .

"The more many Americans have found out about Palin, the less they like her."

Meanwhile, the poll also suggests Americans may not be as concerned as McCain about one-party rule if Obama is elected president.

One of McCain's closing arguments has been that the Democrats are poised to increase their majorities in Congress, and that Obama -- the Democratic presidential nominee -- is "working out the details" with Democratic leaders to raise taxes, increase spending and "concede defeat in Iraq."

But in the poll, 50 percent of likely voters said if Obama wins the White House, Congress should be controlled by Democrats, with 48 percent saying it should be controlled by Republicans.

Fifty-nine percent said if McCain wins the presidential election, Congress should be controlled by Democrats, with 39 percent saying Republicans should control it.

Democrats currently have a 235 to 199 majority in the House of Representatives and a 51 to 49 majority in the Senate -- the chamber's two independent senators are allied with the Democrats.

One of Obama's closing points is that McCain would carry out George Bush's policies if elected, saying the Arizona senator has "ridden shotgun" with the president on economic policy.

The poll suggests that 53 percent think McCain would mostly carry out Bush's policies, with 45 percent saying he would not.

Only 28 percent approve of the way Bush is handling his job as president.

Likely voters questioned in the poll were also asked whether Obama will win the election. Watch more on the final days of campaigning »

"Nine in 10 think it's likely; nearly half say it is very likely. Only 1 in 10 say it is very likely that McCain will win, while half say a McCain victory is unlikely," Holland said.

How will Obama supporters react if he does not win on Tuesday? According to the poll, one in five will be angry; one in four will be upset but not angry. Most Obama supporters, however, say they will be disappointed but not angry or upset if McCain wins.

The poll also suggests the Democrats are much more excited about this election than Republicans. Forty-five percent of Democrats questioned said they are extremely enthusiastic about voting this year, compared to 28 percent of Republicans.

"The economy remains the No. 1 issue to most voters. But although 8 in 10 say that economic conditions are poor now, 62 percent say that the economy will be in good shape a year from now," Holland said. "The economy, which is already a strong issue, jumped even further in importance after the financial crisis hit in September.

"And since the public tends to blame the Republicans more than the Democrats for that crisis, that event provided a boost not just to Barack Obama but to Democratic candidates across the country. Democratic congressional candidates have a 9-point lead in the 'generic ballot' question."

The generic ballot asks voters their preference for U.S. House without naming the candidates running in each district.

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 ranges from plus or minus 3 percentage points to plus or minus 4.5 percentage points, depending on the question.

All About John McCain • Barack Obama • U.S. Presidential Election • Sarah Palin