But governing is much more complicated than campaigning, and as often as not, if the promise is broken, it's because reality has set in. Even in a dictatorship, the guy in charge isn't always able to get done what he wants to; in a democratic republic, there are many more obstacles.
Constitutional checks and balances, conflicting interests, political log-rolling, shifts in public opinion - these and other constraints face an elected official. So the candidate's promises, no matter how genuinely sincere they may have been, become difficult to keep.
This doesn't mean we should let them get away with it. They should be reminded as often as possible of what's been left undone.
If a politician changes course, he or she is invariably accused of flip-flopping. This may be an unfair contention.
Yes, many politicians do flip-flop in order to pander to certain interests or consistuencies, which is reprehensible, but sometimes, it's in response to changing circumstances or new insights.
What some see as flip-flops may indicate careful weighing of options, revisiting decisions, and a willingness to remedy mistakes. Infallibility isn't quite what we the people should demand of our leaders.
All other things being equal, I prefer a politician with an open mind, who remains flexible, to one who is rigid and unwavering. Consistency is not always a plus.
The choice at the polls is not necessarily a test of the candidates' sincerity vs. cynicism, or flexibility vs. rigidity, but of the capacity of us voters - and our willingness - to determine the difference.
Don Harrison is a longtime Philadelphia newspaper editor and writer. He can be reached at firstname.lastname@example.org.