In August 2008, then-Sen. Barack Obama marched out to the roar of a jam-packed Denver stadium to accept his party's nomination for president as almost 80,000 people looked on.
Obama's speech at the 2008 Democratic National Convention was historic -- not only because he was the first black nominee for any major party, but also because he gave the only open-air stadium acceptance speech at a convention since John F. Kennedy did it in 1960.
This year, Democrats were again looking to make an impression by hosting the first convention that both opened and closed with free events for the public. But a last-minute venue change for President Obama's headline speech Thursday from outdoor to indoor dampened part of that vision.
Democrats' convention festivities kicked off Labor Day with CarolinaFest 2012, a free, public street fair in downtown Charlotte, N.C. In January, organizers announced they were cutting official convention business down -- from four days to three -- to make room for the festival.
The convention's climax is planned Thursday, when President Obama officially accepts his party's presidential nod. His speech was originally slated for Bank of America Stadium, rain or shine, with tickets available to the public free through a "community credential" process.
But this morning, plans took a turn when convention officials announced they were moving the speech indoors, citing weather concerns. Obama campaign officials today said there was a 30 percent chance of isolated thunderstorms in Charlotte that night.
Instead of a 73,000-seat stadium packed with grassroots supporters, the acceptance speech will take place at the much-smaller Time Warner Cable Aena, which seats 20,000.
"This is not a Panthers game, as you may know. It's a national special security event," said Obama campaign spokesperson Jen Psaki. "The criteria used for that is ensuring that we're not putting the public safety or security of anybody in the audience at risk."
She added that convention officials might have had to evacuate the stadium if a storm hit.
The majority of tickets -- distributed through local Obama campaign offices on a first-come, first-served basis -- went to North Carolina residents, with a guaranteed spot for any North Carolina or South Carolina resident who volunteered nine hours or more on the campaign, according to convention officials.
As of this morning, campaign organizers said 65,000 delegates and members of the public had already activated the credentials, with 19,000 more people on a waiting list for tickets.
But with the change in venue, only the 21,000 official convention ticket holders will be able to attend the president's acceptance speech in person. Members of the public who applied for and received community credentials will not be honored at the arena. Instead, convention officials said, the president will address ticket holders in a conference call Thursday.
"65,000 people are very disappointed right now that they're not going to be able to come see the president of the United States tomorrow night," an Obama campaign aide told ABC News reporters today.
Among those disappointed would-be speech watchers were Madeline Frank, 16, and her 14-year-old brother, of Charlotte, N.C. Although she's not old enough to vote herself, Frank said she and her brother volunteered 18 hours to the Obama campaign this summer to earn their community credentials for President Obama's speech.
"I've been looking forward to this for a really long time," Frank told ABC News' Sunlen Miller today. "I definitely feel like they should not have promised all these people tickets if there was a chance that we couldn't actually use them."
Republicans were quick to seize the last-minute venue change as a way for Democrats to hide lackluster support for President Obama's re-election bid.
"Democrats continue to downgrade convention events due to lack of enthusiasm -- this time they are moving out of Bank of America/Panther stadium," said RNC spokeswoman Kirsten Kukowski, according to ABC News' Devin Dwyer. "Problems filling the seats?"
Some Romney campaign aides took to the Twittersphere, indicating that Democrats' claims of severe weather reports were overblown.
"What happened 2 rain or shine?" Romney spokeswoman Andrea Saul tweeted, according to ABC News' Devin Dwyer and Michael Falcone.
As of today, Thursday's weather forecast for Charlotte read, "Humid. High 86F. Winds SW at 5 to 10 mph. Chance of rain 40 percent," according to Weather.com.
In Tampa, the only members of the public who attended the four-day Republican National Convention were the 10,000 GOP volunteers already in place, according to convention officials.
"A lot of that is based on security concerns," said Ken Jones, president and CEO of the 2012 Tampa Bay Host Committee. "Given the nature and the security of the event, it's very difficult to do truly wide-open events."
Some political observers said the choice to include the public or not in convention activities is simply a matter of preference.
"I don't think it says Republicans are closed to the public and the Democrats are more open to it," said John Geer, chairman of the political science department at Vanderbilt University.
Conventions are almost a "four-day political advertisement," he said, and it's important for each party to get its message out as effectively as possible.
For Obama, a public event to replicate his iconic 2008 acceptance speech might be just the ticket to boost post-convention ratings and re-energize supporters.
"A huge crowd like that, with a speech that he'll obviously have worked on a lot -- he'll hit it out of the park, because that's what he's good at," Geer said.
But though Obama will have made back-to-back convention speeches open to some of the public, that doesn't necessarily mean Democrats are setting a precedent yet.
"[If Obama loses], they'll re-think everything they did," Geer said. "If it works, it's likely to be continued, but it really depends."
Convention organizers said they will email community credential ticket holders today with dial-in information to President Obama's conference call Thursday.
An Obama campaign official said today that ticket-holders who are shut out from seeing the speech Thursday will "all get a personal touch from this campaign" over the next few months, reported ABC News' Devin Dwyer.
ABC's Devin Dwyer, Michael Falcone and Sunlen Miller contributed to this report.