Journalist Marc Ambinder is leaving DC, and on his departure he wrote a pretty good listicle on what he's learned in his time here. His piece goes relatively easy on our nation's capital when it comes to its moral and spiritual depravity, but he makes some excellent points, including this:
Consistency is not a terribly interesting or useful proxy for effectiveness in a politician, and yet it seems to be the value held most high—or the value that, because someone is most easily able to convince you that someone else lacks it, becomes important. Politicians and the media haven't developed the vocabulary to explain how positions evolve.
Marc is absolutely right about this. You don't have to be a flip-flopper of Romnulan (I'm trademarking that word, by the way; feel free to contact me for licensing opportunities) proportions to fear the consequences of anything that looks like inconsistency; even the slightest deviation from what you've said previously can be punished. Yet how many of us think exactly the same way about every issue that we did a decade or two ago? Not only do people change, circumstances change as well, often in ways that ought to make us reevaluate our positions. It would be nice if every once in a while a politician would say, "I used to believe X, but it turned out I was wrong. So now I don't believe that anymore." It's not that it has never happened—a few people came out and said that about the Iraq war (perhaps most notably John Edwards, back when he was a stand-up guy). But the assumption is that if you do that, then there's a good chance your career will be over, or at least it will be very costly.
There is a logic to consistency. Every time we vote, we're taking an educated guess about how a politician will act in the future. Even if we have a handle on everything a candidate believes today (which most of us don't), there's no telling what new issues could come up once she takes office. So if she has a few iron-clad principles she has promised never to waver from no matter what, at least we'll know what she will and won't do, and we can accept her or reject her on that basis.
Nevertheless, there's no reason that changing your mind in and of itself should be seen as a failure or a betrayal. But it is. And personally, I blame the people. We get the politicians we deserve, just like we get the entertainment, literature, and religion we deserve. If you're reading this website, you're highly interested in and informed about politics. So: when was the last time a political ad or a particularly deft piece of spin changed the way you thought about an issue or led you to vote for a candidate you had previously rejected? Never, right? If every American was as smart as you, every political consulting firm would go out of business.