Barack Obama has George Clooney and Mitt Romney has — Donald Trump.

Donald Trump (Joshua Roberts — Reuters)

“Donate today and you are eligible for a chance to win: Airport transportation in the Trump vehicle;” a “stay at the Trump International Hotel & Tower New York;” a chance to “tour the Celebrity Apprentice Boardroom;” and an opportunity to “dine with Donald Trump and Mitt Romney,” reads the message on the Romney campaign Web site.

An image on the site tells visitors to “donate $3 and you are entered for a chance to win” — although, as the fine print notes, as with any such campaign offer, no purchase is necessary to enter or win a prize.

In addition, Trump is hosting a Romney fundraiser next Tuesday night at the Trump Hotel in Las Vegas. Former House speaker Newt Gingrich (R-Ga.), who dropped out of the race last month, is also expected to attend, according to spokesman R.C. Hammond.

The event is one of two major Romney fundraisers that Gingrich will be hosting, according to Hammond. The second is scheduled for June 11 in Atlanta, Ga., where Gingrich is expected to introduce Romney and where the former House speaker raised a significant amount of money during the GOP primary.

Trump endorsed Romney at a February event in Las Vegas, where the celebrity mogul touted Romney as a candidate who is “tough,” “sharp” and “smart.”

But while Trump remains popular among some in the GOP base, his backing cuts both ways for Romney, as Trump has embraced the “birther” conspiracy theory that Obama was not born in the United States.

Just this week, Trump tweeted: “I wonder if @BarackObama ever applied to Occidental, Columbia or Harvard as a foreign student. When can we see his applications? What do they say about his place of birth.”

So, just how excited are Romney and Trump to be campaigning together? Well, at least one member of the duo seems enthused about the upcoming event.

“As a counter to the Obama-George Clooney event, Mitt Romney has yet again called upon Mr. Trump to provide a little bit of excitement and star power for supporters of Gov. Romney. ... Donald Trump has been the single most significant surrogate for Governor Romney and has pledged his continued assistance to ensure that Obama is limited to being a one-term president,” Trump’s top political aide, Michael Cohen, told ABC News.

Obama, meanwhile, isn’t slowing down the pace of his celebrity events -- according to a fundraising letter sent out to supporters last week, actress Sarah Jessica Parker is hosting an event with Obama and first lady Michelle Obama at her home on June 14.

“Donate $3 or whatever you can to be automatically entered to win,” the Obama campaign e-mail reads.

Staff writer Philip Rucker contributed to this report.

This story has been updated.