WASHINGTON — Even as his turn on the global stage hit an emotional peak Thursday with a speech before a cheering crowd of more than 200,000 in Germany, Barack Obama faced new evidence of stubborn election challenges back home.
Fresh polls show that he has been unable to convert weeks of extensive media coverage into a widened lead. And some prominent Democrats whose support could boost his campaign are still not enthusiastic about his candidacy.
Several new surveys show that Obama is in a tight race or even losing ground to Republican John McCain, both nationally and in two important swing states, Colorado and Minnesota. One new poll offered a possible explanation for his troubles: A minority of voters see Obama as a familiar figure with whom they can identify.
Republicans are moving to exploit this vulnerability, trying to encourage unease among voters by building the impression that Obama's overseas trip and other actions show he has a sense of entitlement that suggests he believes the White House is already his.
In Ohio on Thursday, McCain hit that theme: "I'd love to give a speech in Germany . . . but I'd much prefer to do it as president of the United States, rather than as a candidate for the office of presidency."
Obama also faces discontent from some of Hillary Rodham Clinton's most ardent supporters, who are put off by what they describe as a campaign marked by hubris and a style dedicated to televised extravaganzas.
Susie Tompkins Buell, a major Clinton fundraiser, said: "The Clinton supporters that I know are bothered by these rock-star events. These spectacles are more about the candidate than they are about the party and the issues that we care about."
Obama is to return home Saturday after a nine-day trip that has produced some of the most memorable images of the campaign. Speaking in Berlin before a sea of young faces, the presumed Democratic nominee echoed a famous line from President Reagan, who, at Brandenburg Gate, implored Soviet counterpart Mikhail S. Gorbachev to "tear down this wall."
"The walls between races and tribes, natives and immigrants, Christian and Muslim and Jew cannot stand. These now are the walls we must tear down," Obama told the warmly enthusiastic crowd in Tiergarten park. He spoke from a stage constructed near the Victory Column, a soaring monument to Prussian military triumphs.
Powerful as the image was, back home some voters wondered whether the trip was necessary. Both Obama and McCain had been invited Thursday to a cancer forum organized by cyclist Lance Armstrong's foundation at Ohio State University.
McCain showed; Obama did not. Some in the crowd took notice.
Ann Marie Jones, a stay-at-home mother whose 10-year-old son was diagnosed with cancer in September, said she had leaned toward Obama "until he didn't show up tonight."
"I feel like I understand what he's doing over there, but I think he needed to be here tonight for this," she said.
Jones, a 40-year-old Republican from Aledo, Texas, said she was troubled by the duration and scale of Obama's overseas trip. "I think we have a lot of things going on with our children -- many different things going on here in the United States that need our attention."
Many voters still seem to be puzzling over who Obama is, even after a race that has lasted a year and a half. By 58% to 47%, voters identify more with the values and background of McCain, the presumptive Republican nominee, than with Obama, according to a newly released Wall Street Journal/NBC News poll.
Obama may also be slipping in some key states. He lost a narrow lead in Colorado, falling 5 percentage points in the past month, and now trails McCain 46% to 44%, a new Quinnipiac University poll found. In Minnesota, Obama fell 8 percentage points, though he still leads McCain 46% to 44%, the survey found. The polling spanned the five days before Obama went abroad and the first four days of his trip.
At a time when nearly three-quarters of Americans believe the nation is on the wrong track, the political climate would suggest that McCain, whose party controls the White House, might lag by large margins. Yet a national Fox News poll released Thursday showed that Obama's 4-point lead over McCain in June had shrunk to a single point. The new Journal/NBC poll showed Obama leading by 6 points, unchanged from the month before.
The race remains close even though McCain has stumbled at times and has been largely eclipsed this week by Obama's high-profile trip to Europe and the Middle East, including Iraq and Afghanistan.
On Thursday, television images showed Obama addressing the throng in Berlin, his speech carried live on cable news networks. McCain, meanwhile, spoke to reporters outside an Ohio fudge shop, where his comments were nearly drowned out by wind chimes.
But Obama is struggling with a different set of obstacles; he has yet to lock in some of Clinton's most devoted supporters and active fundraisers.