ACCEPTING your party's nomination to run for president in an outdoor football stadium packed to the gills with 75,000 screaming partisans, chanting your name in a red, white and blue spectacle with music by Stevie Wonder and a fireworks finale . . .

That's a good thing, right?

Maybe.

Even before Barack Obama made American political history in Denver last night by becoming the first black candidate to win a major-party presidential nod, a debate was raging over his choice of Invesco Field, the massive home of the NFL's Denver Broncos, for his big speech tonight.

Supporters of Obama's chief rival, presumptive Republican nominee John McCain, even pounced on a wire-service photo of the preparations yesterday at Invesco, calling the gray columns of the stage "the Temple of Obama" in a campaign e-mail.

The McCain camp is eager for anything that will play into its claim that the Obama campaign is more about show business than substance.

The Politico Web site reported last night that senior Democratic officials are nervous about the stadium plan, which was decided before the GOP began attacking Obama as a narcissistic celebrity.

"We already know he is a rock star; we already know he can bring 85,000 people together in a stadium," Tennessee Gov. Phil Bredesen told the Web site. "He has done it multiple times. He needs to talk to people who haven't made up their minds yet."

G. Terry Madonna, a pollster at Franklin & Marshall College, acknowledged that there's a big risk for Obama in shifting his speech from the Pepsi Center, where the rest of the convention was held. But he said there's also a huge potential upside.

"The plus side is that he'll be outside at an event with [75,000] people, and it will be an electric atmosphere," said Madonna, who said it could seem comparable to a Super Bowl for those who aren't yet focused on the White House race.

Speaking outdoors raises another issue: New kinds of security risks.

News accounts earlier this week on the arrest of three men on weapons violations reported that the men had a high-powered scope that could be used to fire a shot from a long distance.

Authorities later discounted reports that the men had intended to harm Obama, but the security concern is real.

Further upping the ante on tonight's speech is the fact that Obama is locked in a dead-heat race with McCain and has yet to register the bounce that major-party candidates typically receive in the polls during and immediately after their convention.

The first three days in Denver were meant to take care of the other items on the Democrats' sprawling agenda - to tie McCain to unpopular incumbent President Bush while showing unity between the bitter primary rivals, Obama and Hillary Clinton, who appeared again at the convention last night to make Obama's nomination unanimous by acclamation.

Then it was Bill Clinton's turn, and he did something that his wife had failed to do on Tuesday: He spoke directly about Obama as someone who is prepared to become president despite just four years in the U.S. Senate.

"The long, hard primary tested and strengthened him, and in his first presidential decision, the selection of a running mate, he hit it out of the park," Clinton said last night. "Barack Obama is ready to lead America and restore American leadership in the world."

But Obama's acceptance speech tonight will be the real test for millions of viewers.

The lucky throng at Invesco Field - tickets to the speech have been gone for weeks - will also get some big-name entertainment, as soul legend Stevie Wonder is slated to warm up the audience.

A rumored appearance by Bruce Springsteen - also a big Obama supporter - won't happen, leaving many to wonder whether he was asked to stay away in the wake of the GOP attacks that Obama is the candidate of celebrities.

A story in yesterday's New York Daily News said the Obama camp is determined to keep any A-list Hollywood celebrities off the stage at Invesco tonight, which might fan that issue.

Interviewed yesterday on CNN, Republican strategist Leslie Sanchez displayed the party line when she said of Obama: "He's got to get away from just having lofty rhetoric. It's going to be difficult enough that he's in this stadium where he's going to look like a celebrity already, this big rock star with these big, broad words."

Her comments sparked a sharp debate with the CNN host, Soledad O'Brien, who said that a large adoring crowd is what any candidate wants. She said, "I think it's a photographer's dream if the message you're trying to send is, hey, if 75,000 people in this stadium support this guy, why don't you?"

Ezra Klein, blogging for the liberal American Prospect magazine, wondered if there might be a little less to the Invesco controversy than meets the eye.

"My sense is they have their reasons beyond simple sound of the crowd," he wrote. "Maybe it's as simple as 75,000 tickets allows for more organizing opportunities in Colorado. Maybe it's a broader thematic tie-in. Guess we'll know soon enough." *