Hollywood may seem like a completely different world than the White House, but some of Hollywood's most glamorous residents have been breaking away from the red carpet to brush shoulders with presidential hopefuls.

Celebrities have been coming out en masse to publicly endorse a candidate, assist with campaign events and help raise funds. Oprah Winfrey may have been the first high-profile supporter, but the list has expanded to hundreds of stars -- including Barbra Streisand, Hugh Hefner, Jennifer Aniston, Sylvester Stallone and George Clooney.

Candidates are using the high-profile status of these stars to draw the spotlight to themselves. Just this month, U.S. Sens. Hillary Clinton and Barack Obama called on celebrity supporters to help campaign in Indiana. Making recent appearances were musician John Mellencamp, actor Ted Danson and singer Smokie Norful.

Political scientists have long debated whether these types of celebrity endorsements translate into additional support.

"The science of it is really not settled," said James McCann, professor of political science at Purdue University. "The reason for that is it's very difficult to address the question of whether celebrity endorsements come to an already strong candidate or if the endorsement is what helps them become strong. It's the chicken-egg question."

Although there is little research regarding whether the endorsements actually draw support, candidates use the tactic for other reasons, such as gaining publicity. In order to maximize their time in the spotlight, candidates tend to unveil endorsements one by one.

McCann also said support from diverse figures can show the electorate that the candidate has a wide reach.

"It's a way to show you're not a niche candidate and that you have broad appeal," McCann said. "Endorsements can assist a candidate in showing the plurality of that support."

Clinton, especially, has used this technique, receiving endorsements from prominent African-American figures such as Maya Angelou, Magic Johnson and 50 Cent.

Although Obama's celebrity support does not provide the same crossover element that Clinton's does, he has received several political endorsements from individuals who worked closely with former president Bill Clinton -- including the former president's 1992 campaign chairman, David Wilhelm.

One of the other major reasons candidates use Hollywood stars is for their deep pockets. In September, Obama received $3 million from a fundraiser hosted by Winfrey. With the help of singer Elton John, a fundraising event earlier this month helped Clinton bring in $2.5 million.

Several other celebrity fundraisers have brought millions of dollars into each candidate's campaign, with the admission fee at many of the events being $2,300 per person -- the maximum donation allowed under campaign laws.

When it comes to collecting Hollywood money, the Democratic candidates far outpace their GOP opponents. Republican candidate U.S. Sen. John McCain has garnered support from only a few celebrities, such as actor Sylvester Stallone and reality television star Heidi Montag.