The presidential candidate showed off his guitar and played a bit with the band, as picketers protested the return of “The Tonight Show with Jay Leno” to the air in the midst of the WGA strike.

Huckabee spent a great deal of time talking about his plan to replace the IRS, his life living in a trailer while he was governor of Arkansas and the money gap between him and Mitt Romney.

Leno asked him about Monday’s press conference in which Huckabee announced that he would not run an attack ad on Romney — then he ran it for the members of the media.

The media “were very cynical about it, but the point is, if we hadn’t shown it, they would have said, ‘You didn’t have an ad. You’re just bluffing us.’ If I had really wanted to be disingenuous what I would have done is run the ad for three days and then said, ‘Oh, I have a conscience now. I think I’m going to pull it.”

He said that he decided against running it because “we had gotten where we are by being positive and talking about what this country needs to be rather than what’s wrong with the other guys, and I just said…I needed to take a shower or something like that or give Romney a shower maybe. I don’t know.”

The audience laughed at the comment.

The WGA immediately issued a statement expressing “disappointment” that he agreed to appear.

“The Writers Guild is disappointed that Mike Huckabee crossed the WGA picket line today at NBC. We welcome the statements of support he has made for striking writers, but we ask him to respect our picket lines in the future and urge the media conglomerates to return to the bargaining table to make a fair deal that will put writers and the entertainment industry back to work.”

Huckabee said he didn’t realize that Leno had not come to an agreement with writers.

Although the WGA issued a statement earlier today praising Huckabee for expressing support for the writers, and hope that he wopuld not cross pickets, chief union negotiator John Bowman was a bit more circumspect.

“Huckabee claims he didn’t know,” Bowman told the AP. “I don’t know what that means in terms of trusting him as a future president.”

The AP also has a play-by-play of how Huckabee came to discover that he’d be appearing on a picketed show.

“Earlier Wednesday, 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.

“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,” Huckabee told reporters traveling with him Wednesday from Fort Dodge to Mason City.

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

Told he was mistaken and that writers had cleared only Letterman’s show, 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, Huckabee murmured, “Hmmm,” and, “Oh,” before answering another question.”

The complete transcript is here: