(CNN) -- It seems a certainty that the biggest headlines coming out of Tuesday night's CNN debate in Las Vegas will be about race, gays, religion or immigration. It has to be, because only Herman Cain is gaining any traction on Mitt Romney, and it is as much for his freshness as it is for his ideas.
Last week, both Romney and Cain showed they were going to own the debate on the economy. Little air was left for anyone else on the subject. And this week's CNN/ORC Poll shows that it worked for them.
So how do the others gain? By challenging them on the old standby Republican primary issues: those of the social order, of course.
Given the stuff that Cain has said -- that he wouldn't hire a Muslim, he wants to zap immigrants like bugs if they try to get over the wall from Mexico, and blacks only vote for Democrats because they are brainwashed -- there is plenty of fodder to rile him up. And mess him up. Not because most Republican primary voters don't agree with him, but because his inflammatory messages will ricochet differently in the media if he repeats them as a front-runner.
Then there is Mitt. On an anti-gay scale of one to 10, with Michele Bachmann and Rick Santorum registering zero and everyone else but Jon Huntsman earning perhaps a two, only Romney has flipped-flopped up and down the scale. We now know that Bachmann's small business -- which she co-owns with her husband and is always touting -- is actually a clinic that takes people's money with a promise to cure them of homosexuality. Perhaps it would work equally well to cure Romney of his hatred of his own views about gays. And Romney has just as scratchy a record on abortion.
Nevada is a touchy place to debate immigration. The large Latino population votes mostly Democratic, and the state has long depended on immigrant labor. And we saw from Sharon Angle's failed race for the U.S. Senate in 2010 that immigrant bashing might get headlines, but it doesn't get enough Nevada votes. I predict that Tuesday night, the candidates will go for the headlines.
Then there is the third rail of religion. What will Cain trip up on tonight? Hiring Muslims? Vying with Rick Perry to be the best at avoiding a defense of Romney's freedom of religion? Can Perry get into the conversation at all? Or is he really bearing too much resentment from being brutalized by his opponents for his evangelical Christian faith, as his wife recently said? He is sure to challenge Cain and Romney's credentials to represent the evangelical and tea party wings of the Republican Party.
Yes, Tuesday night's debate is going to matter Wednesday, mostly because of the issues that divide the U.S. Let the red meat be thrown.
The opinions in this commentary are solely those of Hilary Rosen.