So much can change during the course of a few weeks. Since the last Republican presidential primary debate on Sept. 22, Herman Cain has become the party’s latest “flavor of the month” and has the commensurate polling numbers to prove it. Meanwhile, Texas Gov. Rick Perry, September’s favorite, has seen his numbers plummet, due in large part to a series of poor performance debates.

The two presidential hopefuls have the most to prove and to lose in Tuesday night’s debate, sponsored by Bloomberg News and The Washington Post. According to a new Marist poll of likely Republican primary voters in New Hampshire, where the debate will take place, Cain tied with Rep. Ron Paul for second place with 13 percent among likely Republican primary voters in New Hampshire, while Perry garnered just six percent of support.

The forum will focus solely on the economy, which Perry has claimed is his greatest area of strength. But can the formerly strong debater provide the kinds of responses that will inspire confidence in conservatives or will he “throw up on himself,” as bewildered pundits said he did the last time? That will be his biggest test. In addition, he will likely face questions about the racist name on a hunting retreat his family leased and continued attacks on immigration, particularly a policy that allows the children of illegal immigrants to attend Texas’ public universities and pay in-state tuition.

Former Republican National Committee chairman Michael Steele says that most people can forgive Perry for not having the finesse of a Bill Clinton or a Barack Obama, and Perry’s biggest challenge will be to make a compelling case for his positions that will resonate with the audience.

 “In this case it’s immigration, primarily, and how he’s expressed his views on the issues that have put him at odds with the base that three weeks ago was adoringly pushing him into the race and celebrating his entry,” said Steele. “Now he’s pretty much at the bottom of the political barrel. For him, tonight is about getting back up on that horse and riding strong and standing firm on what he believes and making the case for those beliefs.”

Cain also has a lot riding on the debate. As he joked during the Values Voter Summit Friday, as a frontrunner “you get this bull’s-eye on your back.” He will face far more targeted questions about his 9-9-9 flat individual, corporate and sales tax rates and be forced to defend it in a much more detailed and prescriptive manner. He also may be treated more harshly than in the past by the candidates he has eclipsed in the polls who, like Cain and Perry, are fighting to become the anti-Romney and win the hearts and votes of conservative voters.

(Photos: Richard Ellis/Getty Images; Spencer Platt/Getty Images; Alex Wong/Getty Images)