The findings underscore the difficulties ahead for Democrats as they hope to retake the White House during a time of war, with voters giving McCain far higher marks when it comes to experience, fighting terrorism and dealing with the situation in Iraq.
Both Barack Obama and Hillary Rodham Clinton have made ending America's involvement in the war a centerpiece of their campaigns. And even though a clear majority of those polled said the war was not worth waging, about half of registered voters said McCain -- a Vietnam vet who has supported the Bush administration's military strategy -- was better able to deal with Iraq.
In head-to-head contests, the poll found, McCain leads Clinton by 6 percentage points (46% to 40%) and Obama by 2 points (44% to 42%). Neither lead is commanding given that the survey, conducted Feb. 21-25, has a margin of error of plus or minus 3 percentage points.
The Arizona senator is viewed favorably by 61% of all registered voters, including a plurality of Democrats.
The survey showed that McCain's potential advantages extend even to domestic issues, where he is considered to be most vulnerable. Even though McCain has joked about his lack of expertise on economic issues, voters picked him over Obama, 42% to 34%, as being best able to handle the economy. However, Clinton led McCain on that issue, 43% to 34%.
"I just think he's older, he's more experienced, and he's got the betterment of the country in mind," said Robert Fear, 79, a registered Democrat from Newton, Ill., who said he planned to support McCain in November.
In the Democratic race, the survey showed, Obama's support has increased across all of the party's key constituencies.
The Illinois senator now leads Clinton, 48% to 42%, among Democratic primary voters nationally -- a far cry from his double-digit deficits throughout 2007 and the first weeks of 2008.
The poll, which surveyed 1,246 registered voters, was conducted under the direction of Times Polling Director Susan Pinkus.
Obama's lead over Clinton in the Times/Bloomberg poll comes in the wake of his 11 consecutive primary and caucus victories. He is ahead in the closely contested race for delegates to the party's national nominating convention and in recent days has made gains in the key states of Ohio and Texas, which hold primaries Tuesday.
At least two other national surveys released this week have shown Obama taking the lead among Democratic voters -- a development that puts further pressure on Clinton to win the upcoming primaries or face calls from some party leaders to drop out.
One hopeful sign for the New York senator: Of Democratic voters whose home states have yet to hold primaries or caucuses, the former first lady maintains a 13-point edge over Obama.
But the findings also showed that Obama has successfully broadened his coalition, which once was limited primarily to wealthier and better-educated Democrats.
While Clinton's support has remained steady at 42% since the last Times/Bloomberg survey, in January, Obama's has surged 15 points. That may be due to backing from voters who had supported John Edwards -- who dropped out of the race Jan. 30 -- as well as many previously undecided voters.
Obama now splits the vote with Clinton among Democratic primary voters without college degrees and among working women, two areas in which Clinton had been strong.
But the findings showed that whoever wins the nomination could face challenges in unifying the party. Older white women remain fiercely loyal to Clinton, while the contest has revealed a sharp race gap -- with blacks overwhelmingly supporting the man who could become the country's first African American president.
The poll suggests that the once-muscular grip on the Democratic base held by Clinton and her husband, the former president, has loosened quickly as they have intensified their attacks on Obama and tried to paint him as ill-prepared for the presidency.
One of the most striking findings is that when Democratic voters are asked whom they support now, regardless of whom they voted for in an earlier primary or caucus, Obama leads by nearly 20 points, 55% to 37%.