Paul Greenberg

Sometimes turning points in presidential campaigns are scarcely noted at the time. Because they're events that didn't happen, a low road not taken, a tactic not employed, a decisive mistake not made. Like last week's non-event in Mitt Romney's presidential campaign.

Told of a great big, $10 million mudball some of his backers were prepared to throw at his opponent, Mr. Romney said no thank you. Very much.

Naturally, the plan was leaked to the New York Times, the country's leading source of news that never happened, and in this case isn't about to.

Invited to revive the issue of Barack Obama's ties to his old firebrand of a pastor back in Chicago, even the billionaire backer of a Romney Super PAC had the good sense -- and good taste -- not to touch it. Wise decision.

Here was an opportunity to replay the 2008 presidential election -- and its result. Some opportunity. Mr. Moneybags turned it down, blaming the whole, awful idea on some unnamed political consultant.

But before he did, the candidate himself nixed the scheme. In no uncertain terms. "I repudiate that effort," said Mitt Romney. "I think it's the wrong course for a PAC or a campaign."

But he didn't stop at just rejecting the idea; he offered a better one. Instead of the past, he said, he hoped this year's presidential campaign could be "about the future and about issues and about vision...." Instead of looking backward, he was urging the country to look forward. It's the American way.

Successful presidential campaigns aren't just a matter of rousing speeches and glittering promises, but what the candidate declines to do -- what he cannot bring himself to do.

Call this non-event the case of the mud that was not thrown. It's of a piece with Sherlock Holmes' dog that did not bark.

The unobservant may think something that didn't happen is of no interest. On the contrary, it may be the most telling of clues. In the Holmes story, a police inspector from Scotland Yard who is consulting with our hero asks:

"Is there any other point to which you wish to draw my attention?"

To which our ace sleuth in the deerstalker cap responds: "To the curious incident of the dog in the night-time."

But, the good inspector points out, "The dog did nothing in the night-time."

"That," explains Holmes, "was the curious incident."

Mitt Romney did nothing about this bad idea some mastermind in the bowels of his Super PAC had come up with -- except to denounce it. That was the curious incident in last week's campaign news.

Paul Greenberg

Pulitzer Prize-winning Paul Greenberg, one of the most respected and honored commentators in America, is the editorial page editor of the Arkansas Democrat-Gazette.