Today’s debate is the most important yet of Herman Cain’s campaign. He’s tied or leading Mitt Romney nationally. One poll has him with an eight-point lead in Iowa, he is way ahead in South Carolina, only five points behind in Nevada, and three behind in Florida. The next debate is not until November 9, so if he performs well he’ll have a significant amount of time to rally the anti-Romney vote behind him.

Herman Cain’s candidacy is defined by his 9-9-9 plan: Bring down 9-9-9, bring down Cain. You can guarantee that his admission that 9-9-9 will raise taxes on some people will be used against him.

His misjudging of the housing bubble may be brought up. Rick Santorum has been criticizing Cain for saying he’d let states make their own decisions on gay marriage. Cain may also be attacked for his opposition to stricter drinking and driving regulations when he was the head of the National Restaurant Association.

The last debate focused solely on the economy, so Cain’s lack of knowledge of foreign affairs wasn’t an issue. This time will be different, especially in light of the Iranian terror plot. When asked about stopping a nuclear Iran, he said that only a pre-emptive strike would work — but he’d have to first consult with advisors. This shallowness won’t cut it in a debate, especially with the sophisticated policy proposals of Rick Santorum and Newt Gingrich on the issue, who favor regime change.

Cain better show up with detailed numbers to defend his 9-9-9 plan, and he would be wise to boast that he’s a mathematician. He can blunt attacks on his national security credentials by mentioning his past work on weapons systems — which he has inexplicably still failed to mention — and by taking on Ron Paul.

He should also mention the poll that shows him defeating President Obama by two points, in order to undermine the electability argument central to Romney’s campaign.

Mitt Romney is still in a very good position. He’s leading in New Hampshire, Nevada, Florida, and according to some polls, Iowa. The attention is on Herman Cain, allowing Romney to continue his strategy of letting other candidates throw punches for him. If Romney’s past performances are any indication, this will be another good night for him.

Newt Gingrich is cementing his third-place position, though Rick Perry isn’t far behind. At least two polls show him in third nationally (though others have him as low as fifth place). He’s in third in Iowa and Florida, so he will benefit from Perry’s continuing downward slide and any slip-up by Cain. However, his huge debt restricts his ability to capitalize on this momentum, and the transition from policy analyst to presidential candidate is proving difficult for him. To date, he still has yet to explicitly say why he’s the best candidate on stage, and although he has substantive ideas, he has to convince voters that he’s the guy to implement them.