While vacationing in his native Hawai'i, Barack Obama said he wanted to enjoy some local cuisine — a plate lunch, shave ice, the noodle dish Zip Min — and relax with a little bodysurfing "at an undisclosed location."

Good for him. Obama needed the rest and refueling. He has a lot of work to do at the Democratic National Convention, which begins in 10 days. The presumptive presidential nominee has at least three Herculean tasks awaiting him in Denver.

First, he has to win over the Hillary holdouts, especially those women over 50 who think he's more style than substance and insist that he only got this far because the male-run media sabotaged the first woman with a serious shot at the White House. Those women treat Obama like the flashy pretty boy they warned their daughters about. Some of them pressed to put Hillary's name in nomination at the convention.

Next, Obama needs to use the convention to dispel lingering doubts about who is he and where he would lead the country, if elected. That is the one thing missing from an otherwise well-run campaign. Maybe Obama is too cerebral and needs to show more emotion. And, like Bill Clinton and George W. Bush did in their election campaigns, he needs to let down his guard and invite us into his private life. It could make him more likable — and more real.

Finally, Obama must again confront a suspicion that he probably thinks he dispelled months ago when he disowned the Rev. Jeremiah Wright and his Trinity United Church of Christ. Not a chance. Many Americans still have an unfortunate and unfounded prejudice about Obama not being "American enough." Background too exotic. Name too foreign. Religion too cloudy. It all plays into the fear that Obama cannot be trusted because, supposedly, his allegiance lies elsewhere.

It gets absurd in a hurry. Even Obama's choice of vacation spots makes him suspect, according to a nearly incoherent Cokie Roberts on ABC's "This Week." While the journo-pundit was graciously willing to acknowledge that "Hawai'i is a state," she also insisted that Obama's vacation there "has the look of him going off to some sort of foreign, exotic place" — this from a woman who should know better because she grew up in the wonderfully foreign, exotic city of New Orleans.

Mark Penn speaks the same code. A recently surfaced memo that Hillary Clinton's former chief political strategist sent to the candidate in March 2007 shows that Penn was more than ready to launch a cultural strike against Obama. That meant playing on people's fears and painting Obama as someone "who is not at his center fundamentally American in his thinking and in his values." Such creepiness makes you wonder whether Penn has any values.

Note the irony. All this talk about Republicans allegedly playing the race card against Obama, and it was a Democratic operative who was ready and eager to do some real damage by dabbling in demagoguery and dropping "the American card."

Minorities should remember the Penn memos, especially since — according to new population projections by the U.S. Census Bureau — they will soon be coming into greater prominence. The Census estimates that minorities will be the majority in America by 2042, or eight years ahead of earlier projections. Such a dramatic change on the horizon was bound to stir fears, and it has. Check out the immigration debate, which is fueled not by concerns over border security or economic competition but by insecurities over the changing face and the shifting culture of America.

It's that insecurity that Penn wanted to tap into with his evil plan to paint Obama as a foreigner and that Hillary Clinton — even though she rejected that advice — made a play for with her comments to USA Today about how she did better than Obama with "hardworking Americans, white Americans." It's that insecurity that lets some people think that a person of color born into less-than-privileged circumstances, who studied hard, took risks and lived the American Dream, is any less American than anyone else. And it's that insecurity that Obama has to confront in Denver once and for all.

To do that, he has to continue hammering away at what being an American means to him and how his life story, and America's story, go together like, well, a plate lunch and shave ice.

Ruben Navarrette Jr. is a columnist and editorial board member of the San Diego Union-Tribune, He is the author of "A Darker Shade of Crimson: Odyssey of a Harvard Chicano." Reach him at ruben.navarrette@uniontrib.com.