In U.S. history, I can think of just two presidents (there may be others) who were remarkably good at defying the paradoxical pattern: George Washington and James K. Polk.
Washington levitated above all partisan infighting and campaigning because of his stature as the founding father of them all, a man who could be trusted with power because of his demonstrated willingness to surrender it. His predictability in that regard alone might have earned him the position of first among equals in the American pantheon. Polk, in the campaign of 1844, promised a reduction of the tariff, resolution of Oregon's borders and the acquisition of California. He achieved them all, did everything that he said he would do, then stepped down and died three months later, his legacy for consistency secure.
As the primaries and caucuses proceed through Iowa, New Hampshire and on to Nevada and South Carolina, we'd be foolish to believe there was a Washington or even a Polk on the ballot. All that we can responsibly ask of the voters in those states -- who are likely to define our choices in the general election -- is to decide on a course they think the country should follow, vote accordingly, then say a prayer. Because, as they say, you never know.
-Presidential candidates pledge a lot, but history says you can ignore most of it.