Obama's overseas trip, which was widely seen as a success, has not enhanced perceptions of his effectiveness as a commander in chief. Just 20 percent of those surveyed say Obama is "very likely" to be an effective commander in chief, down 4 percentage points from last month. McCain is seen as "very likely" to be effective by 38 percent of respondents, down eight points from last month but still significantly ahead of Obama.
The most important issues for voters, however, are domestic: 36 percent of registered voters cite the economy and jobs as their top concern, easily eclipsing the war in Iraq at 17 percent. Gas and oil prices were cited by 9 percent of registered voters, followed by health care at 8 percent and the environment at 5 percent. A substantial majority of those surveyed - 70 percent - say the candidates are not doing enough to address their top issue.
Indeed, voters appear overwhelmingly concerned with the home front: Seventy-seven percent of registered voters say the next president should focus more on domestic issues than foreign policy issues. Just 8 percent say the next president's primary focus should be international issues.
McCain and Obama fare about equally when it comes to voter perceptions of how they will handle the economy. Fifty-two percent of registered voters say they are either "very" or "somewhat" confident that Obama will make the right decisions on the economy; fifty percent are "very" or "somewhat" confident McCain will.
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And voters believe the next president can make a difference. About two in three say a president can "do a lot about" both the national economy and the price of gasoline.
Americans' assessment of the economy remains grim. Eighty-three percent describe the condition of the economy as "bad," and the number who describes the economy as "very bad" has increased to 43 percent, up from 35 percent last month. Nearly two-thirds of those surveyed say the economy is getting worse.
Obama's lead over McCain is built on stronger support from Democrats, liberals, African Americans, voters under age 45 and women. Most former supporters of Hillary Clinton are backing Obama, as are a plurality of working class whites, a group Obama struggled to attract during the primary.
McCain leads among conservatives, Republicans, white evangelicals and voters age 45 and over. The presumptive GOP nominee has a narrow lead with men and with whites.
Independents are evenly split between the two candidates.
About one third of those voters who prefer one of the candidates say they have not yet completely made up their minds. But while this group is roughly evenly split between McCain and Obama supporters, an enthusiasm gap remains: Obama's supporters are three times more likely to be enthusiastic about their candidate.
About two in three McCain supporters say they are "satisfied" with the Arizona senator, though 17 percent say they are "dissatisfied." Just six percent of Obama supporters are "dissatisfied" with their candidate.
More than half of registered voters say they are paying "a lot" of attention to the campaign.
Obama's favorable rating has fallen 2 points, to 37 percent; his unfavorable rating stands at 32 percent. He still leads McCain on this front, however: The Arizona senator is viewed favorably by 33 percent of registered voters and unfavorably by 34 percent.
McCain does have slightly more credibility than his rival: Slightly more than half of registered voters say Obama says what voters want to hear instead of what he believes; a smaller percentage, 44 percent, say they same of McCain.
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Thirty percent said that the candidates' choices of their running mates will have a great deal of influence on their decision. That's twice the number who said vice presidential picks would matter in 2000, when George W. Bush and Al Gore were preparing their campaigns. (Read more on that part of the poll here.)
Iraq, China And President Bush:
McCain has an edge on handling the war in Iraq. One in four voters are "very confident" McCain will make the right decisions on Iraq, while just 14 percent say the same of Obama.
More than half of registered voters are at least somewhat confident that Obama will make the right decisions on Iraq, however. And while 47 percent are "not confident" that he will make the right decisions, that percentage is just slightly higher than percentage who say the same of McCain (43 percent).
Nearly half of those surveyed say the troop surge, which McCain supported, is making things better in Iraq, up from 17 percent in June of last year. Forty-five percent say things are going well overall for the U.S. in Iraq, while 49 percent say things are going badly.
Most Americans (62 percent) think the recent economic expansion in countries like China and India has been bad for the U.S. economy. Just 14 percent say the growth has had a positive effect.
Nearly two in three say President George W. Bush should attend the Beijing Olympic Games, as he plans to do. Twenty-eight percent say he should avoid the games due to China's record on human rights.
Just 7 percent of Americans see China as an ally. A majority - 60 percent - say the country is friendly, but not an ally. Twenty-three percent describe China either as unfriendly or an enemy.
President Bush's approval rating stands at 25 percent, equaling his all-time low reached in June.
CBS News re-interviewed voters who said they were uncommitted, including those who had a candidate but said their minds could change, when we first spoke with them in a CBS News/New York Times poll in mid-July. In the July poll, that was about 36 percent of all registered voters.
The most recent round of interviews suggest that these uncommitted voters remain largely up for grabs.
Seven in ten remain uncommitted. And while a quarter of this group now say they have made a commitment to a candidate that they don't think will change before the election, about as many as a month ago don't have a candidate choice at all yet.
This group seems to have become less interested in the campaign since last month. When asked in mid-July how much attention they'd been paying to the 2008 campaign generally, 45 percent said they'd paid a lot. When asked in this poll how much attention they'd been paying in the last few weeks, only 18 percent reported paying a lot of attention.
This poll was conducted among a random sample of 1,034 adults nationwide, including 906 registered voters, interviewed by telephone July 31-August 5, 2008. Phone numbers were dialed from RDD samples of both standard land-lines and cell phones. The error due to sampling for results based on the entire sample and for registered voters could be plus or minus three percentage points. The error for subgroups is higher. For the uncommitted voters section, CBS News re-interviewed 331 uncommitted voters first interviewed by CBS News and the New York Times July 7-14th 2008. This poll was conducted by telephone August 1st - 5th 2008. Error due to sampling for results based on the entire sample of uncommitted voters could be plus or minus five percentage points. Error on measures of individual change is much smaller.