Asked in last month’s Iowa debate about his proposal for a 20-foot barbed wire fence along the border, Herman Cain responded with exasperation -- “ America has got to learn to take a joke!”

The former Godfathers’ Pizza CEO is undoubtedly the funniest Republican candidate. Now he has to prove he can be more than a comedian.

Cain’s easy way with words has been attracting big crowds in Iowa. So far, that interest hasn’t translated into broader support. He finished fifth in the Ames Straw Poll -- behind Rick Santorum. He’s languishing in polls.

Given its scarcity of money and staff, any chance for the longshot candidate to speak on a nationally-televised stage is a victory for the Cain camp. Cain argues that his off-the-cuff style is part of his refreshing, anti-Washington appeal. But if the outsider wants to have any impact on the race, he will have to start showing a more serious side.

If Cain can make headlines from tonight’s debate for something other than a wisecrack, he will have succeeded. If he can’t, it will serve as another sign that his campaign itself may have a long ways to go before it is taken seriously .