What happens when an irresistible force meets an immoveable object?That's one question raised by the 2016 presidential campaign.

You win the presidency, Richard Nixon supposedly observed, by tacking to the right in the primaries and to the center in the general election. Hillary Clinton seems to be following that strategy except, as a Democrat, she is tacking to the left.

Not all important public policy reforms come from Washington. Really lasting reforms can percolate from the bottom up, brewed by citizens with a grievance pushing state and local governments to act.

Sherlock Holmes famously solved the mystery of the Silver Blaze by noting the dog that didn't bark in the night. It strikes me that in this wild and woolly campaign cycle there have been numerous dogs not barking in the night, or in the daytime either. 

In November 1964 a crowd of 5,000 attended the opening of the Verrazano Narrows Bridge, then the longest suspension bridge in the world. Presiding were New York Mayor Robert Wagner, Gov. Nelson Rockefeller and transportation and parks czar Robert Moses. Also in the crowd was a teenager named Donald Trump.

Scott Walker's abrupt withdrawal from the Republican presidential race Monday afternoon shows how different, in ways noticed and unnoticed, this campaign cycle is from those of recent years.

As the 2016 presidential selection process proceeds, there is increasing evidence that the political patterns we have grown used to, that we have come to consider permanent, might be suddenly changing.

In this presidential cycle, voters in both parties, to the surprise of the punditocracy, are rejecting experienced political leaders. They're willfully suspending disbelief in challengers who would have been considered laughable in earlier years. 

I've seen this movie before. And for the last 25 years, I thought I'd never have to watch it again. But now it's playing not in theaters, but all over mainstream media, with something like rave reviews from the president and his administration.

Aside from the court-ordered dribbling out of Hillary Clinton's classified-material-filled emails, the big presidential campaign news of the summer has been the boom for Donald Trump in the race for the Republican nomination.