As the Democrats head into their convention, should they be singing the Eurythmics 1985 hit "Here Comes That Sinking Feeling"?

Just as party leaders pack their bags for Denver, our latest Reuters/Zogby poll finds their nominee in some trouble, as Republican John McCain has taken a five-point lead over Barack Obama. That is a 12-point reversal from the survey we took for Reuters in July.  Interestingly, Obama's margins among what had been his strongest demographic groups dropped by as much as 12 points. These include Democrats, women, city dwellers and younger voters - those ages 25-34. Also, Obama has lost his lead among the swing Catholic vote, dropping 11 points to McCain over a month.

What is happening is all too familiar to Democrats. McCain is using the Karl Rove playbook, attacking Obama's perceived strengths, notably his mass appeal and freshness. Democrats hoped that eight years of a failed Bush presidency (80% in our latest survey said the nation was on the wrong track) so diminished the GOP brand that "going negative" would not work again for the Republicans.

In the end, it may not. Negative campaigning did not work on either side of the aisle in the primaries and caucuses. However, clearly McCain has been the aggressor for the past month, seeing an opportunity to define Obama for General Election voters before Obama could define himself. At times, it has seemed like he has been the only one throwing any punches, especially with Obama on vacation in Hawaii.

The adulation of European crowds on Obama's overseas trip seems to have helped McCain with conservatives. They distrust Europeans and actually had the opportunity to imagine a liberal Democrat in the role of President - and didn't like the thought. Meanwhile, Obama's attempts at flexibility on issues dear to liberals and young voters (Iraq and FISA) may have dampened their enthusiasm.

Choosing August for a vacation proved inopportune for Obama. August has been cruel to Democrats in the past. That is the month when Jimmy Carter, Mike Dukakis and John Kerry all went down in the polls.

As much as voters may prefer the Democrats on most issues, McCain is winning the contest of defining who has the character and personality that swing voters expect in a President. Obama appeals to the mind. McCain goes for the gut.

McCain's war record and well-established image as a maverick Republican make it tough for Obama to assail McCain the man. Obama's rhetoric this week shows he recognizes that his issues appeal must become more aggressive and emotional. With 48% of our poll respondents citing the economy as the most important issue, Obama is hitting hard at the GOP record on job losses. He clearly has work to do. Our Reuters/Zogby poll released Wednesday shows more voters trust McCain to deal effectively with economic issues.

Obama must convince voters that he is on their side. While it may be difficult to measure, race complicates that task with white voters, especially older people. Some believe that McCain has already injected racial innuendo into the campaign. The non-partisan David Gergen said on ABC: " . . . as a native of the south, I can tell you, when you see this Charlton Heston ad, 'The One,' that's code for, 'he's uppity, he ought to stay in his place.' "  Obama partisans also saw race as the subtext of two McCain ads:  one that featured Brittany Spears and Paris Hilton, and another that showed several young white women praising Obama.

But when Obama responded to these ads by saying McCain was trying to frighten voters, and adding that he did not look like other Presidents on dollar bills, voters judged Obama negatively and felt he was the one bringing race into the campaign.

It may happen that independent expenditure groups - those so-called "527s" - will raise the racial ante. If they do, Obama may be forced to follow the model set by Jackie Robinson, who ignored taunts in order to succeed as Major League baseball's first African-American.

His vice-presidential pick and the convention now give Obama the opportunity to restore his image as an agent of positive change who would inspire the nation to act. It will be a tall order. But let's not forget - it was the electric Obama speech at the Democratic convention four years ago that got this whole presidential campaign started in the first place.

Paul Lomeo is a senior writer with Zogby International, and for many years worked in public affairs on labor and reproductive rights issues.