WASHINGTON, DC (CBS) -- Donald Trump is stirring up questions about the President's citizenship ahead of a fundraiser tonight with Republican White House hopeful Mitt Romney. It comes just as Romney is getting ready to clinch his party's nomination.

Campaigning in Colorado, Mitt Romney went after President Obama for his handling of the economy. Romney says, "The president, when he got elected said, 'I'm going to go out and borrow $787 billion, nd I'll keep unemployment below 8 percent. It has not been below 8 percent since."

It's the message that helped Romney outlast his Republican competition. And Tuesday primary voters in Texas are expected to give the frontrunner the delegates he needs to become the GOP's nominee.

But Romney won't be celebrating there; he's campaigning in the swing state of Nevada and raising money in Las Vegas with Donald Trump.

The real estate mogul continues to question President Obama's citizenship - stirring controversy for Romney. He says, "You know, I don't agree with all the people who support me and my guess is they don't all agree with everything I believe in."

The Obama campaign put out an internet video criticizing Romney for not distancing himself from Trump's accusations.

The ad includes the President's 2008 opponent John McCain defending the president's citizenship.

Donald Trump upped the ante on Twitter Tuesday saying the President is using John McCain the ads because McCain lost his bid for the White House. White House spokesman Jay Carney says, "We could revisit that but I think the American people are fed up with this kind of nonsense."

President Obama was born in Hawaii and last year the State released his long form birth certificate.

Four years ago President Obama did not sew-up the Democratic nomination until June 3rd. Romney beat that by a few days, but it took him longer than any recent Republican candidate to reach 1,144 delegates.