Political conventions these days are less about choosing a candidate than they are well-orchestrated shows aimed at getting the party's message and candidate out to the country.
Just Tuesday, Obama raised nearly $5 million at a celebrity-packed fundraiser in Los Angeles. The same day, George Clooney pulled in up to an additional $900,000 for the Democratic candidate at a fundraiser of American citizens in Switzerland.
"The two things you need to win are money and people's attention, and celebrities can get you a little of both," said Steve Ross, chairman of the history department at the University of Southern California.
While celebrities have donated plenty of money to campaigns, their real value comes in the ability to draw crowds.
"Once people turn out, they actually listen to the campaign speech," said Ross, who is finishing a book called "Hollywood Left and Right: How Movie Stars Shaped American Politics."
Democrats have traditionally had a larger showing of stars and this year is no different. Celebrities from Oprah Winfrey to Ben Affleck to Kareem Abdul-Jabbar have come out in support of Obama.
The Republicans have had their fair share of stars too, with Heidi Montag, Stephen Baldwin, Wilford Brimley, Kelsey Grammer, Jon Voight and Sylvester Stallone all backing McCain.
But overall, the television, film and music industries have been leaning heavily toward Democrats this year, according to an analysis by the Center for Responsive Politics.
Obama received more than $4.8 million and Hillary Clinton, his main challenger in the Democratic primaries, took in another $3.6 million from the industries as of Aug. 20.
McCain got less than $900,000.
The actual donations from movie stars make up just a small amount of the overall cash needed to run for president. Consider this: Obama has raised $389 million to date and McCain has taken in $174 million.
"The biggest givers in politics are not celebrities," said Massie Ritsch, spokesman for the center. "They are most commonly Wall Street bankers, lawyers, lobbyists and corporate executives."
It's just that celebrities tend to get more attention than other donors, Ritsch said.
"If anything," he added, "they are probably most valuable to a campaign as headliners for fundraising events that bring in more donors."
Democratic fundraiser Donna Brazile said celebrities are visible and help attract support that isn't otherwise always available to candidates.
"As technology expands how campaigns are both covered and managed, celebrities can help well-known candidates appear like ordinary people," she said in an e-mail. "In the final days of the Gore campaign, Bon Jovi traveled nonstop with the candidate on a tour of Michigan. People came to see Gore, but also hear Bon Jovi. What a two-fer for any candidate seeking both the spotlight and to raise much needed funds."
"When celebrities do anything, people pay attention," Robert Thompson, director of the Bleier Center for Television and Popular Culture at Syracuse University, said. "It's one of the ways you can shoehorn yourself into more media attention."
Thompson equates the political endorsements to what those celebrities do for sneakers, sports drinks and cars.