The 64-year-old also pressed his case that President Barack Obama may have perpetrated "one of the greatest scams in the history of politics, and in history period," by being elected president without being born in the country.

This time, he hawked discredited accounts that his grandmother had witnessed his birth in Kenya. Trump offered the notion that he has "people" in Hawaii trying to find his birth certificate, "and they cannot believe what they are seeing."

The will-he-or-won't he Trump sideshow has been a minor story in still-inchoate campaign for the Republican nomination for president in 2012, but it is threatening to move center stage.

A Wall Street Journal/NBC News poll found that in a broad field of Republican candidates, former Massachusetts Gov. Mitt Romney came in first with 21 percent, with Trump and former Arkansas Gov. Mike Huckabee tied for second with 17 percent.

Trump has said he will decide whether to run in early summer, but he will be ubiquitous until then. When the Republican Party of Iowa announced he would headline its Lincoln Dinner June 10, the switchboards lit up.

"I love this country, but this country is going to hell," he said on the "Today Show." "I would run a great, great country."

"The world laughs at us," Trump said Thursday. "They won't be laughing if I'm president."