Updated

Days before the Democratic Convention begins, Barack Obama has a slim 42 percent to 39 percent edge over John McCain in the race for the White House, according to a FOX News poll released Thursday.

A month ago Obama led by 41 percent to 40 percent. Both leads for Obama – this month and last – are well within the margin of sampling error.

• Click here to view full results of the poll (pdf).

Opinion Dynamics Corp.conducted the national telephone poll of 900 registered voters for FOX News from August 19 to August 20. The poll has a 3-point error margin.

Obama leads McCain among women (43 percent – 37 percent), voters under age 35 years old (55 percent – 32 percent) and black voters (74 percent – 7 percent).

McCain has the advantage among white voters (44 percent – 37 percent), voters 65 years and over (42 percent – 35 percent), white Evangelical Christians (55 percent – 26 percent) and among men by just one point (42 percent to 41 percent).

Among independents, it’s a toss up: Obama tops McCain by just 31 percent to 30 percent, with 28 percent undecided and 8 percent saying they will vote for someone else. Last month, Obama had a 34 percent to 32 percent edge (July 22-23, 2008).

McCain has slightly stronger backing from his party: 82 percent of Republicans support him compared to 78 percent of Democrats that support Obama.

It’s more than two months before the election and many voters are still undecided – 14 percent in this poll. To find out more, the poll asked these voters why they were unsure. Some 27 percent of undecided voters said they would like to vote for the Democrat but have questions about Obama, and 20 percent of undecideds would like to vote for the Republican but have questions about McCain.

In a hypothetical matchup, Hillary Clinton tops McCain by 46 percent to 43 percent.

Large majorities of both Obama voters (85 percent) and McCain voters (86 percent) say they are “certain” to vote for their candidate. How certain? The poll asked these voters if they would still vote for their candidate even if he were, hypothetically, to announce a drastic policy change on a specific major political issue.

Most (68 percent) of Obama voters would still vote for him if he changed his position on abortion to pro-life. In addition, a 58 percent majority of Obama’s supporters would stick with him even if he announced he intended to appoint conservative judges like Antonin Scalia to the Supreme Court.

The only issue that caused more voters to defect than stay was on foreign policy. If Obama changed his position and said he was ready to go to war with Iran, 41 percent of Obama voters would still vote for him, while slightly more — a 44 percent plurality — would not.

About one of four Obama voters is extremely loyal and would still vote for him if he made all three policy changes.

What would it take for McCain to lose his supporters? More than two-thirds (68 percent) say they would still vote for McCain if he became pro-choice, and a 52 percent majority would stay with McCain if he said he would appoint liberal judges like Ruth Bader Ginsburg to the Supreme Court.

Even if the Republican changed his position on Iraq and said the U.S. should withdraw troops immediately, 55 percent of McCain voters say they would still vote for him.

Among Evangelical Christians supporting McCain, 72 percent say they would still vote for him if he became pro-choice on abortion, 62 percent would stay with him if he changed his position on Iraq, and 50 percent would stick with him if he said he would appoint liberal judges.

Overall, three in 10 McCain voters would stick with him even if he made all three of these drastic policy shifts.

The Comfort Factor

One in three voters would be “extremely” (12 percent) or “very” (21 percent) comfortable with McCain as president, 37 percent “somewhat” comfortable and 28 percent “not at all” comfortable with the Arizona senator in the Oval Office.

For Obama, more than four of 10 voters would be “extremely” (15 percent) or “very” (26 percent) comfortable with him as president, another 25 percent would be “somewhat” comfortable and almost a third (31 percent) say they would not be comfortable at all with Obama as the country’s leader.

When facing the “toughest decision of your life,” by 43 percent to 37 percent more voters would ask McCain for advice than Obama. Some 18 percent of Democrats and 41 percent of independents would go to McCain for advice, while 7 percent of Republicans would go to Obama.

By a slim 42 percent to 41 percent voters would pick McCain to run a company they own.

Top Issues

By far, the economy (43 percent) is the top issue on the minds of voters, followed by the Iraq war (11 percent), health care (9 percent) and terrorism (9 percent).

On handling specific issues, Obama is trusted more to handle health care (+ 17 points), the economy (+ 9 points) and energy independence (+ 8 points). McCain is trusted more to handle terrorism (+ 20 points), illegal immigration (+ 8 points) and Iraq (+ 7 points).

Voters are much more likely to say they think McCain is better qualified than Obama (49 percent to 30 percent) to handle the conflict between Republic of George and Russia. Furthermore, a 54 percent majority thinks it is likely there will be a new cold war with Russia.

Candidates Viewed Favorably

Both Obama and McCain are rated positively by voters. A 59 percent majority views Obama favorably, about the same as his 58 percent favorable last month, and 35 percent have a negative view.

For McCain, 60 percent have a favorable view of him, up from 54 percent in July, and 34 percent unfavorable.

What do voters like “most” about Obama? In unprompted, spontaneous responses the most often mentioned traits were: new ideas, change, young, good speaking ability and knowledgeable.

Characteristics voters like most about McCain: experienced, military background, qualified, knowledgeable, and honest and trustworthy.

What voters say they like “least” about Obama include: too young/inexperienced, flip flops, disagree on issues generally, he’s a Democrat/Liberal, dishonest, and radical/anti-white/Rev. Wright.

And for McCain the main reasons cited for disliking him were: too old, too close to Bush, he’s a Republican/Conservative, supports Iraq war and he flip flops.