George Clooney and Michelle Obama at dinner. Actor George Clooney sits beside first lady Michelle Obama during the State Dinner for British Prime Minister David Cameron at the White House in Washington (Reuters/REUTERS)

President Obama’s widely publicized fundraiser with actor George Clooney is shaping up to be a Hollywood blockbuster.

A May 10 dinner at Clooney’s Studio City, Calif., home has sold out at 150 guests, who are expected to jointly contribute between $5 million and $6 million toward Obama’s reelection effort, people familiar with the event said. They asked not to be named because they are not authorized to speak publicly.

In addition, the Hollywood Reporter cites sources saying that the campaign expects to have raised as much as $6 million more in online donations, which were solicited as part of a nationwide contest to win a ticket to the dinner.

A haul of $12 million would arguably make the soiree the biggest single presidential fundraising event in U.S. history. Campaign sources are throwing cold water on the estimated total from Internet contributions, however, as being too high.

The Obama campaign declined to comment. Demand for tickets to the Clooney event was so intense that organizers attempted to limit attendance to residents of Southern California, the Hollywood paper reported.

The frenzy of interest echoes Obama’s record-breaking fundraising effort in 2008, when massive rallies and donor events became routine. Obama is particularly focused on donors in the entertainment and technology sectors this time around because of his troubles raising money on Wall Street.

But the Clooney event also comes amid escalating attacks from Republicans on Obama’s celebrity status. American Crossroads, a conservative group advised by GOP political guru Karl Rove, released a web video last week mocking Obama's “cool” reputation as representing style over substance.

“After four years of a celebrity president, is your life any better?” the ad asks, as Obama is shown hugging late night TV host Jimmy Fallon.

The 2008 Republican nominee, Sen. John McCain (R-Ariz.), tried a similar line of attack in the last presidential race.

The Clooney event is just one example of the Obama campaign’s aggressive and often creative fundraising tactics, from dinners with the president to ads featuring the family dog, Bo.

The campaign relentlessly publicized an “Obama, Clooney and You” fundraising contest that ended Monday, bombarding supporters with e-mails, text messages and tweets urging them to donate $3 or more and sign up for a chance to attend the dinner. (Like all such political contests, participants do not actually have to give money to enter the raffle.)

“By pitching in before midnight, you’ll automatically be in the running to join me and George Clooney at his place on May 10th,” Obama said in an e-mail to supporters on Monday. “It’s not often I can get away from work, so I look forward to spending a fun evening in L.A. with a couple supporters like you.”

Most of those in attendance will give a lot more than $3, however: Up to $40,000 per person to Obama’s campaign and related political committees. If all 150 guests give the max, the total would hit $6 million.

In addition to stumping for Obama, Clooney is a regular celebrity presence in Washington and has become a key activist in connection with the emerging humanitarian crisis in South Sudan.

Romney is hosting his own series of fundraising events in an attempt to catch up with Obama, who had 10 times as much cash on hand at the end of March. The Romney campaign expects to post strong fundraising numbers for April, however, which is when the former Massachusetts governor became the presumptive Republican nominee.