Presidential candidates parachute into Las Vegas weekly. But they don't come here intending to actually answer questions. They drop by a school or a union hall for carefully planned rallies. Pictures are taken, safe questions from safe questioners get safe answers, the candidates smile ... and then they're gone.

Here's the secret everyone knows: Presidential campaigns are like kabuki theater -- highly stylized and scripted. We caught a rare glimpse of what happens when the script goes wrong last week in Iowa, when Sen. Hillary Clinton's campaign got caught planting a question at a town hall meeting.

In what was staged to look like a spontaneous, give-take Q&A session, Sen. Clinton called upon Grinnell College student Muriel Gallo-Chasanoff, who asked about global warming. Hillary said young people always ask her about global warming and then proceeded to give her standard global warming campaign answer.

Then came a non-scripted political moment of clarity.

Ms. Gallo-Chasanoff blurted to reporters that she was put up to the question by Hillary's staffers. "They wanted a question from a college student," Gallo-Chasanoff said.

"One of the senior staffers told me what (to ask)."

After initially denying it, the Clinton campaign admitted to planting the question, but said Hillary herself didn't know anything about it and the campaign would never, ever plant a question again.

This is political fibbery, of course. Obviously Hillary was in on the planted question. The reason "young people" always ask Hillary about global warming is because Hillary's staff makes sure a young person always asks her about global warming. Duh.

And, don't think for a minute that this is going to change anything. The Clinton campaign will go right on scripting appearances down to the last details and, when needed, planting specific questions, just as Barack Obama's campaign does it, and John Edwards' campaign does it, and Rudy Giuliani's campaign does it, yada, yada, yada.

History has proved the dangers of going off-script.

Most recently, Howard Dean did it with his goofy rally scream, and that's all it took to send him packing. If you're lucky enough to have lived a while, you'll remember Edmund Muskie's emotional defense of his wife at an impromptu news conference on the doorstep of a newspaper in New Hampshire. Reporters said he cried. He said the "tears" were melted snowflakes.

Whatever.

The bottom line was that the unscripted episode ended the presidential ambitions of a man who woulda-coulda-shoulda beat Richard Nixon in 1972.

This is also why most presidential candidates avoid hanging around newspapers, particularly if it involves the editorial boards of newspapers. The last thing campaigns want is to get their candidate into a room with independent questioners from the Review-Journal, who not only can ask tough questions with follow-ups, but also print the results overnight to a half a million people in Las Vegas.

The Review-Journal's editorial board is open to all candidates, major and minor. So far, GOP Rep. Duncan Hunter has dropped by. So has New Mexico Gov. Bill Richardson, a Democrat. You can read what I thought of Richardson in my May 6 column, which is accessible through the Review-Journal's Web site.

Former Massachusetts Gov. Mitt Romney, to his credit, stopped in Friday and survived the grilling.

I don't know when, or if, the others will show up. We don't beg the candidates to come in, but I always wonder about their intestinal fortitude when they don't.

Perhaps the handlers know that their candidate can't take a tough line of questioning. Or maybe somebody inside the campaign does the math and decides the risk of an unscripted Q&A with independent Nevada journalists isn't worth the reward. That, of course, says more about what they think of Las Vegas voters, than it says about anything else.

Full disclosure: We ask tough questions of all candidates, both Republican and Democrat. No planted questions.

But, I'll tell you what -- if it breaks the ice with Hillary, I'll be happy to allow her first question to be on global warming. She can then show us she has a sense of humor by telling us she always gets this question from young people on the campaign.

But, it's only fair to add that Sen. Clinton may then reliably expect a tough follow-up question or two.

I wonder ... can she take a tough, unscripted question?

Sherman Frederick is publisher of the Las Vegas Review-Journal and president of Stephens Media. Readers may write him at sfrederick@reviewjournal.com.