Campaign Trail Highs. And Lows.

Barack Obama stepped into the concrete pavilion in Chicago to the roar of some 7,000 hometown fans and the Tina Turner anthem of "Simply The Best." If the Illinois senator is the pop star of politics, Sunday night's rally was arena rock. After all of two days as an official presidential candidate, Obama was drawing crowds as big as President Bush did at his final event of the 2006 elections.

"It's good to be back home," he shouted, as his fans screamed. "Goodness gracious!" Goodness gracious? How earnest and wholesome can this rock star be?

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A little too earnest, it turns out. Obama began a lengthy exposition on the failings of the health system and the need for medical records. "They have no paperwork when they take your money," he said to the crowd's delight, "so why is there paperwork when you need health care?"

Then the hecklers started: a group of maybe a dozen young protesters who consider Obama's antiwar position insufficiently antiwar. "We'll talk about that soon," he said reassuringly. But they didn't think that was soon enough. "You made your point," he said more firmly. "Why don't you relax?"

They didn't relax. "I'm talking about health care right now," he explained.

For a few minutes, the hecklers did something extraordinary. They stopped and listened to Obama's call for consensus on universal health care. Then they started shouting again. "What I'm asking for is some courtesy until I get to answer your point," he pleaded. "Just relax."

That's the thing about hecklers in presidential campaigns; they are very discourteous.

Obama quickly hit his stride again, as the hecklers were pushed out of the arena. But the incident opened a short window into a long campaign: the kinds of strains this new candidate will endure, and the tensions that he'll need to resolve.

Campaigns are an intense stress test of a candidate's weaknesses. For Hillary Clinton last weekend it was her reluctance to renounce her vote for the war in Iraq. For Obama it was his inexperience in the spotlight, where the audience can just as easily throw rotten fruit as fragrant flowers.

The hecklers also exposed the tensions inside Obama as a presidential candidate. Some politicians find an easy quip to put down hecklers; others speak over them with all the force of their microphone. But Obama is more idealistic: he wants to earn their respect as he educates the voters—even those who oppose him—about the big issues of the day. In short, he wants to be a respectable and responsible rock star.

In his first two days in Iowa as an official candidate, Obama illustrated the pulling power of such a campaign—and a few of its perils, too. In Cedar Rapids, before an impressively large crowd of more than 2,000, Obama took questions in a town-hall setting. The event started with a moderator who was so impressed by several callers to C-SPAN that he repeated their questions on stage. Fortunately, the audience seemed to fit the C-SPAN model, and they lobbed in their own questions about Iraq, North Korea, the defense budget and the No Child Left Behind education law.

Sure, Obama could spit out a sound bite when he wanted to: "The problem with No Child Left Behind," he said, "is it left the money behind." But as he waded into the weeds of wonkery, it was hard to believe that the pundits were complaining about his lack of substance. "The country is in a serious and somber mood right now," he told the audience. And serious and somber—not punchy slogans or partisan attacks—is what they got.

The next day, at Iowa State University in Ames, the mood had changed. Obama bounced down the stairs of the university arena to the funky sound of the O'Jays singing "Give The People What They Want." One of the signs he passed was a simple hand-written message on a small piece of brown cardboard: WE NEED A HERO. For the 7,000 people who showed up—another enormous crowd, considering that it's a full year before the caucuses—Obama was all they wanted.

But this wasn't a rally marked by heroic perfection. It started with a big endorsement by Iowa's attorney general, Tom Miller. Unfortunately, Miller endorsed Obama for governor, then quickly explained how he had only just run a gubernatorial campaign in Iowa. That's the problem about starting a presidential campaign so early.

Miller didn't stop there. He soon claimed that Obama was "the smartest guy to go to Harvard Law School in the last 25 years." At this point, Obama's wife, Michelle, stepped back in mock horror and glared at her husband, who started waving his hands in denial. So the candidate started the rally with a quick correction. "The smartest person I know who went to Harvard Law School is my wife, Michelle ," he admitted.

But there would be no similarly instant correction for a blunder in Obama's own speech. As he riffed on some of his best antiwar lines, the candidate sounded dismissive about the sacrifice of the troops. "We ended up launching a war that should have never been authorized and should have never been waged," he said, "and to which we now have spent $400 billion and have seen over 3,000 lives of the bravest young Americans wasted."

It was a logical—but insensitive—way to talk about a war that Obama describes as "a tragic mistake." Later, in a newspaper interview with the Des Moines Register, he was at pains to explain how he didn't mean to say "wasted." What he meant to say was that the sacrifice of the fallen troops wasn't matched by "honesty on the part of civilian leadership." Welcome to the campaign trail, senator.

Back in Chicago, Obama told how he had spent the weekend campaigning with his young daughters and their grandmother. At one point, his daughter Malia was asked whether she was having fun. "It's great, it's fun," the 8-year-old girl said. "Why are we here again?"

"Out of the mouth of babes," Obama exclaimed, pretending to be hurt. He spent the rest of the speech trying to answer the question seriously. But it will take him months before he can answer it fully—and flawlessly.