Republican presidential candidate Herman Cain has been rising fast in the polls and has quickly become a target for other candidates to explain his policies.

He is expected to face more intense scrutiny from his rivals during the GOP debate Tuesday night in Las Vegas, Nev.

Cain will join the debate, along with former Massachusetts Gov. Mitt Romney, Texas Gov. Rick Perry, Minnesota Rep. Michele Bachmann, Texas Rep. Ron Paul, former Pennsylvania Sen. Rick Santorum, and former House Speaker Newt Gingrich.

Cain is the former chief executive officer of Godfathers Pizza and a motivational speaker. He said he's been catching on with voters because his solutions are simple and he's got a sense of humor.

"Stupid people are ruining America!" Cain said during an appearance featured in an Omaha, Neb., press club video.

"Imagine there is no pizza. I couldn't if I tried.," he sang in a mocking rendition of the John Lennon song, "Imagine."

Cain has already had to apologize for some of the comments he made over the weekend regarding immigration.

While some in the GOP are attracted to Cain's unorthodox campaign, his opponents hope he will not be able to withstand the pressure of being on top.