Sen. Barack Obama delivers his acceptance speech for the Democratic nomination in Denver.

Sen. Barack Obama delivers his acceptance speech for the Democratic nomination in Denver, Aug. 28, 2008.

Paul J. Richards/AFP/Getty Images

DENVER — One of the trickiest aspects of an acceptance speech at the end of a national convention is the choice the presidential nominee must make between the audience in the hall and the vastly larger one beyond.

More than a few presidential nominees have been caught up in the hall dynamic to the detriment of the broadcast connection. Others have too obviously talked over the heads of delegates to the TV cameras, getting out of sync with the eager support group all around them and eventually losing their momentum.

Sen. Barack Obama spoke to both audiences and made it look easy. A massive crowd of more than 80,000 came to hear him in a midsized city on a midweek evening, and they were rewarded with a speech that seemed directed to them. Yet while Obama was talking to delegates in Denver, he also seemed to be speaking to the country as a whole, and even to far-flung but interested parts of the world.

That masterful balancing was one reason the speech seemed to succeed despite expectations far too high to be tamped down. More on this in a moment, but first, let's consider some of the other potential contradictions in the balance as he made his remarks.

"Get tough" versus "new politics." Obama first rose through the ranks of presidential contestants last fall and winter by accentuating the positive and making rare use of attack lines. More recently he has been hitting back at ads designed by his opponents to belittle or besmirch him.

In his acceptance speech, Obama had clearly decided to engage Sen. John McCain more directly than ever before. He even adopted a more truculent tone: "I've got news for you, John McCain, we all put our country first." But he leavened this with a pledge to campaign on issues and not character attacks: "But what I will not do is suggest that the senator takes his positions for political purposes. ..."

"Make it soar" versus "fill in more of the policy detail." Obama has been criticized for buying popularity with a series of gauzy but fine-sounding speeches that offer little substance. His campaign has always disputed this and pointed to Web sites full of gritty and even numbing detail. Still, the national political audience knows Obama more as a motivational speaker who can draw a crowd than as an idea man or effective legislator.

So Obama laid out the beginning of policy prescriptions on capital gains and other taxes (promising to soak only the wealthiest 5 percent and give everyone else a tax cut), health care access and cost, time off for people caring for new children or sick family members. But he did not dwell too long on any one topic — including Iraq — before moving on to the next.

In the final minutes, Obama turned back to the biblical admonitions and poetics that have been a popular trademark of his best speeches: "...and in the words of Scripture hold firmly, without wavering, to the hope that we confess."

"Keep the faith with African-Americans" versus "establish a comfort level with Anglo whites." There's no question this dilemma has been with Obama since he first ran statewide in Illinois, or perhaps from his earliest years in a multiracial family. Obama began his presidential chase de-emphasizing his race, then found states where having race at the center of his campaign was useful. More recently, he has been downplaying it again.

In this speech, Obama saved the outreach to blacks until the end, when he acknowledged the day as the 45th anniversary of the March on Washington for civil rights, the occasion for Martin Luther King Jr.'s "I Have a Dream" speech. It brought the night to its final emotional climax, and brought tears to many of the delegates and others in the stadium.

"Own the space" versus "connect with the TV audience." This particular conundrum, mentioned above, pits the folks in the hall against everyone else who might be interested. The former are a kind of captive audience — it's too crowded to move — and they are presumably at least partly pre-sold or they wouldn't be there. They are also highly visible and audible, and their reaction becomes part of the speech's overall impression.

The larger audience is invisible, amorphous and highly diverse in its politics and interest level. Its members may know what capital-gains taxes are, or have an opinion on nuclear power, or they may not. But one thing is clear: They have a remote control and they know how to use it. Lose them for more than a matter of seconds and they are gone.

This targeting challenge was especially acute for Obama after he and his retainers decided to move the speech out of the Pepsi Center, site of the first three nights of the Democratic National Convention, to Invesco Field at Mile High, the home of the Denver Broncos.

Here, beneath the canopy of a warm and breezy Colorado night, more than 80,000 people were on hand to hear the speech. It was not just an audience capable of absorbing all of a speaker's attention; it was a throng that seemed to demand it. Through a long day of gathering, the crowd remained focused on the magnet that had drawn them there, and by show time the atmosphere of expectation was intense.

The light-and-music show never approached the heights of pageantry seen in — oh, let's say the opening and closing ceremonies of the Olympics in Beijing. Nor did it involve ritual sacrifice or an appearance by Bruce Springsteen. But it was an impressive show by the standards of national political conventions, which should probably also have fireworks (as this event did).

They applauded and cheered at Obama's appearance and at every applause line. They stayed after the speech to sing and dance, despite the sense of loss at the missing balloon drop. The overarching metaphor was of an open party, welcoming not just delegates and political pros (and media) but also vast numbers of ordinary citizens who arrived and attended for nothing.

Even the lights, swinging in wide and interchanging arcs across the dark mass of the crowd, implied an enfolding motion and energy. The brilliant splashes of light kept roving and raking the faces, pulling their attention down to the concentric circles of steps that would retract and leave the new Man of Chicago standing alone. Alone, in the midst of 80,000. A speaker subsuming contradictions and cross-pressures in a single vision, in a single speech.

Whether you buy the vision or trust the speaker, the political artfulness and effectiveness of the speech and the entire event have had few equals in recent American history. If the night fulfills its promise in November, it will be more historic still.

10:11 - August 29, 2008