Byron York

What's wrong with Rick Perry? How did the successful, well-liked, long-term governor of one of America's largest states enter the Republican presidential primary race with great fanfare, zoom to the top of the polls, and then slide almost as quickly back into the pack?

Blaming the Texas governor's problems on a lackluster debating style -- as Perry himself has done after a number of poor performances -- answers only part of the question. Yes, debates are particularly important this campaign season. But debates are more than just style and popularity contests. They reveal deeper things about candidates; voters watching debates can learn not only how a candidate handles tough questions but whether he is really, truly prepared to run for the White House.

Early in Perry's candidacy, there was a spate of stories suggesting he's not smart enough to be president. They weren't subtle; one was headlined "Is Rick Perry Dumb?"

But even Perry's critics could look at those stories and say: Here is a man who has successfully governed a large and complex state, presided over prosperity and growth, dealt with the political challenges that go with it all, and won re-election repeatedly. Successful governorships don't just happen by accident; Perry's results in Texas show he is a smart, competent executive.

But the debates have revealed a different problem. The Rick Perry who has taken the stage in four Republican debates so far is a man who, for all his governing success in Texas, appears not to have thought enough about why he wants to be president of the United States and what he would do if he achieved his goal. When critics gently say that Perry's presentations have been "light on details," they're really saying Perry doesn't seem to have thought things through.

More than anything else, a lot of thinking should precede a run for president. There's no time to think about much of anything once the campaign begins, and there's no way a candidate can collect and organize a lifetime of experiences into a coherent approach to national issues once he's flying from stop to stop. A candidate has to have done his thinking long before he hits the road or steps on a debate stage.

Think back to a different example from a different time. In 2005, President George W. Bush nominated White House counsel Harriet Miers to the Supreme Court. Miers was a perfectly fine White House counsel, but she clearly had not spent a lifetime doing the kind of legal thinking that prepares one for the highest court. The White House assured doubters that Miers planned to study really, really hard in preparation for her confirmation hearings.

Byron York

Byron York, chief political correspondent for The Washington Examiner