The most dramatic event of last night’s Republican presidential debate was the speed with which Rick Perry’s mistake became a campaign gaffe of historic proportions. The National Review’s Rich Lowry wondered if it was “the most uncomfortable moment” he had “ever witnessed in presidential politics.” The University of Virginia’s Larry Sabato had a more definitive take, “To my memory, Perry’s forgetfulness is the most devastating moment of any modern primary debate.”

I don’t think it’s wrong to write-off the Texas governor as a viable candidate for the nomination, but it is wrong to attribute his non-viability to this particular gaffe. If Perry had established himself as an intelligent, composed and serious candidate, then he could afford to have mistakes like these; they’d be seen—rightly—as a one-off occurrence. The problem for Perry is that he’s developed a reputation for undisciplined vapidity. For GOP voters, last night’s performance was a reminder that Perry is unprepared for the rigors and diffiulties of a presidential campaign. In other words, the problem with Perry’s gaffe is that it confirmed a particular narrative—his conservative virtues notwithstanding, the Texas governor isn’t equipped to handle a face-off with Barack Obama.