MASON CITY, Iowa —Michael Huckabee, a presidential candidate sounding a populist theme in Iowa, likely will be forced to cross a writers’ picket line if he appears today on the “Tonight Show” with Jay Leno.

Earlier today, Mr. Huckabee said he supports the writers and did not think he would be crossing a picket line, because he believed the writers had made an agreement to allow late night shows back on the air.

In fact, that is true only of David Letterman, who has a separate agreement with writers for his “Late Show.”

“My understanding is that there was a special arrangement made for the late-night shows, and the writers have made this agreement to let the late night shows to come back on, so I don’t anticipate that it’s crossing a picket line,” Mr. Huckabee told reporters traveling with him today from Fort Dodge to Mason City.

“I support the writers, by the way. Unequivocally, absolutely. They’re dead right on this one. And they ought to get royalties off the residuals and the long-term contracts.”

“I don’t think anybody supports the producers on this one,” he added. “Maybe the producers support the producers, but I think everybody in the business and even the general public supports the writers.”

Told he was mistaken and that writers had cleared only Letterman’s show, Mr. Huckabee protested: “But my understanding is there’s a sort of dispensation given to the late-night shows, is that right?”

Told again that he was wrong, Mr. Huckabee murmured, “Hmmm,” and, “Oh,” before answering another question.