The Republican accusations against Democratic presidential candidate Barack Obama have come fast and thick, from palling around with terrorists to being a tax-loving socialist.

But Obama has proven surprisingly adept at shrugging off rival John McCain's attacks and opinion polls show McCain is the one whose image has suffered from the negativity.

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"Obama has handled himself very calmly and in many ways has seemed steadier than McCain - and McCain has really helped him create that impression," said Andrew Kohut, president of the Pew Research Center.

"He's tried a lot of things. Obama has done a good job of countering them."

Obama's resiliency has surprised Republican strategists who entered the campaign for the Nov. 4 election believing he was vulnerable to the sort of attacks that helped bring down recent Democratic candidates like John Kerry and Al Gore.

Republican consultant Kevin Madden, an aide to Mitt Romney during his presidential run and to President George W. Bush in 2004, said Obama was helped by McCain's failure to settle on a clear line of attack.

Bush hammered Kerry in 2004 as a "flip-flopper" for months until "about 40 days before the election, it kicked in," Madden said. Gore was relentlessly mocked in 2000 as an elitist who was out of step with mainstream America.

McCain, a veteran Arizona senator, flipped quickly through similar attacks and many more in the months since Obama clinched the Democratic nomination in June, never settling on a theme.

"The McCain campaign hit the reset button far too often," Madden said. "Obama emerged from the primaries with a lot of vulnerabilities but making those into liabilities required a very consistent focus that they never developed."

During the summer, McCain mocked Obama as a political celebrity and elitist, criticized his shifting positions and made fun of his penchant for huge rallies and high-flying rhetoric.

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But Republican hopes that Obama, a first-term Illinois senator, could be painted as dangerously inexperienced were negated by McCain's choice of Sarah Palin, the nationally unknown first-term governor of Alaska, as his running mate.

Efforts to portray Obama as too liberal, with a history of associations like his service on a Chicago community board with a former 1960s radical, failed to gain steam as the economic crisis deepened and Obama performed steadily in a series of debates.

McCain's reaction to the financial crisis - he initially called the fundamentals of the economy strong as it teetered then suspended his campaign to work on a bailout but resumed before it was completed - diminished his criticisms of Obama.

'Out of touch with the moment'

"McCain at times has appeared out of touch with the moment," said Simon Rosenberg, head of the Democratic advocacy group NDN. "While Americans are worried about their economic survival, he was talking about a 1960s radical."

Nevertheless, McCain and Palin have cranked up the attacks again in recent days, describing Obama as a socialist for his plans to raise taxes on the wealthy and reduce them for lower-income workers.

They also have tried to link his campaign to allegations of voter registration fraud by the community group ACORN and painted him as risky after the weekend prediction by his running mate, Delaware Sen. Joe Biden, that Obama would face an international crisis in his first six months in office.

McCain's campaign has sponsored automated calls in battleground states stressing Obama's links to Vietnam-era radical William Ayers. At least two Republican senators have asked for the calls to end.

None of the attacks appears to have worked.

A Pew poll on Tuesday showed more voters now express doubt about McCain's judgment than Obama's and see McCain as less inspiring than Obama. A majority say McCain has been too personally critical of Obama.

A Washington Post/ABC poll found majorities of undecided and persuadable voters do not believe Obama's past relationship with Ayers or his campaign's association with ACORN are legitimate election issues.

The Pew poll gave Obama a 14-point lead nationally. Two other polls, by Reuters/C-SPAN/Zogby and NBC News/Wall Street Journal, put Obama's lead at 10 points.

Polls in many crucial states also give Obama an edge as McCain's path to the 270 electoral votes needed to win the White House becomes increasingly difficult.

Republican consultant Rich Galen said McCain had two chances to strike real blows at Obama - after the successful Republican convention and after Obama's speech to an adoring crowd in Berlin made him look like he was chasing global celebrity.

"They couldn't capitalize in either case and they let Obama off the ropes," Galen said. "I don't know that Obama was ever properly tested."