The poll contains troubling signs for Obama as he looks to mobilize the Democratic Party behind him following his long and sometimes bitter battle with Hillary Clinton for the Democratic nomination, however.
Twelve percent of Democrats say they will support McCain in the general election. That's higher than the 8 percent of Democrats who defected to President Bush in 2004. Nearly a quarter of Clinton supporters say they will back McCain instead of Obama in the general election.
McCain leads Obama by 8 points among registered independent voters, considered a key voting block in November. The Arizona senator leads Obama 46 percent to 38 percent, with 11 percent of respondents undecided.
Sixty-three percent of all voters - including more than half of Democratic primary voters - say the length of the Democratic primary battle has hurt the Democratic nominee's chances. Just 27 percent say it has helped the nominee's cause.
Read The Complete CBS News Poll On The General Election
Race And The 2008 Election
The President, Economy And Iraq
Roughly two-thirds of Democratic primary voters think there is a better way: to have a single national primary day instead of the current, staggered timeline.
A majority of Democratic primary voters - 59 percent - say Obama should choose Clinton as his running mate. Clinton supporters are more enthusiastic about the prospect than Obama supporters, who are evenly split on the question of Clinton as a vice presidential pick.
Overall, Obama leads Clinton among Democratic primary voters, though the margin is smaller than last month. Obama leads Clinton 45 percent to 41 percent among the group, down from a 12 point spread last month.
Many voters say former President Bill Clinton's involvement in his wife's campaign hurt the former First Lady. Thirty-nine percent of all voters surveyed say the former president damaged his wife's campaign, while 23 percent say he helped her.
Views Of The Candidates:
McCain is seen as "very likely" to be an effective Commander-in-Chief by more registered voters than either Obama or Clinton. Thirty-nine percent of those surveyed said McCain is "very likely" to be effective, versus 25 percent for Obama and 22 percent for Clinton. However, a majority says it is at least "somewhat likely" any of the three candidates would be effective.
Obama is seen as caring a lot about voters' problems by 38 percent of registered voters, versus just 22 percent for McCain. Both candidates are seen as sharing values by a roughly even percentage of respondents, 63 percent for McCain and 62 percent for Obama.
Obama has a 41 percent favorable rating - down three percentage points from last month - and a 31 percent unfavorable rating. McCain has a 34 percent favorable rating - up two points from last month - and a 37 percent unfavorable rating.
Obama and other Democrats have repeatedly stressed that McCain's policies would essentially mean a third term for Mr. Bush. More than four in ten voters believe McCain would, indeed, generally continue Mr. Bush's policies.
And while about half think McCain would be different from the current President, nearly as many say he will be MORE conservative (21 percent) as think he will be LESS conservative (28 percent).
Sixty-two percent of those asked say McCain's age - he will be 72 on inauguration day - will not impact his effectiveness as president. Thirty percent say it will be an obstacle, while 7 percent see it as an asset.
President Bush's approval rating is at its lowest level to date. Just 25 percent of Americans approve of the overall job Mr. Bush is doing as President, an all-time low for him and among the lowest approval ratings ever recorded for a President.
Sixty-seven percent disapprove of the job Bush is doing - the highest such figure in CBS News polls since he assumed office.
Only Presidents Nixon (24 percent) and Truman (22 percent) have seen polls showing job approval ratings lower than 25 percent during their presidencies, according to Gallup Polls. President Carter's all-time low was 26 percent.
The Economy And Gas Prices:
Thirty-four percent of Americans cite the economy as their top concern, more than any other issue. That's followed by gas prices, cited as the top concern by 16 percent of those surveyed, the war in Iraq, cited by 15 percent, and health care, cited by 4 percent.
Sixty-five percent say that the recent increase in gas prices has caused them financial hardship - and 36 percent say that hardship is serious. Nearly nine in 10 Americans expect gas prices to go up even further over the summer.
Nearly one in five Americans say their income is not enough to pay their bills. Nearly half of Americans say they are making just enough to pay their bills.
Americans have become slightly more optimistic about the economy than they were in May, though they still remain overwhelmingly pessimistic. Twenty percent of those surveyed say the economy is in good shape, up from 16 percent a month ago. Seventy-eight percent say the economy is in bad shape.
Almost 70 percent of those surveyed believe the economy is getting worse; only 3 percent say it is improving.
Eighty-three percent think the country is on the wrong track - the highest percentage in the twenty-five years since CBS News began asking the question. Just 14 percent say things are on the right track.
The War In Iraq:
Americans are more pessimistic than ever about the prospects for a stable Iraq.
Sixty-one percent say Iraq will never become a stable democracy - the highest number since CBS News starting asking the question in December 2003. Just one third think Iraq will become a stable democracy, and most of them think that will take longer than two years.
Thirty-five percent of those surveyed say things are going well in Iraq, down from 40 percent in April. Sixty-two percent say things are going badly.
Americans would like U.S. troops to come home from Iraq sooner rather than later. 42 percent are willing to have U.S troops remain in Iraq for only a year or less. 21 percent say troops should stay for one to two years more, while 30 percent are willing to keep troops in Iraq longer than two years.
This poll was conducted among a random sample of 1,038 adults nationwide, including 930 registered voters, interviewed by telephone May 30-June 3, 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 could be plus or minus four percentage points. The error for subgroups is higher. The error for the sample of registered voters is plus or minus four points.