People seem to think politicians should always be consistent in their viewpoints. A candidate who says something one week, then does or says something inconsistent with it the next week, is seen as a hypocrite, and judged harshly for it.
I love The Daily Show, but it thrives on this. An entire bit can consist of a series of clips showing politicians saying one thing, then the same person three years later saying the opposite thing.1 It's funny, yeah, but does it really tell us anything? Should we trust these politicians less?
I don't think so. I'm more concerned that a position is consistent with reality than with a past position.
In fact, I respect a changing viewpoint more than an unwavering one. A reasoned opinion is based on infromation, and information is constantly evolving. That's not a bad thing, it's a rational thing.
The consistent politician who sticks to their guns despite all evidence to the contrary is closer to a zealot than a strong leader fit to run a country in a rapidly changing world. Flexibility should be admired more than steadfastness.
Maybe it has to do with a reluctance to call anyone wrong. You may vehemently disagree with a viewpoint, but concede that it's "just an opinion," and opinions should persist over time. Someone has to be wrong though. It's one thing to respect other viewpoints, but another thing to fail to acknowledge that viewpoints are based on facts that may or may not be true.
As a concrete example, take gay marriage. Opposition to gay marriage is not just a personal value judgement; it is based on facts, such as "gay marriage hurts traditional marriage," "people choose to be gay," and "an omniscient creator does not approve of it." This opposition may filter through generations and manifest as subjective hate, but its original origin is objective facts, and these facts are either true or they are not.
(Spoiler alert: they are not)
Screw consistency over time. Consistency with reality is what matters. Judge politicians and their parties by their current platform's consistency with and effect on reality, not some nebulous gut need for stability.
"Consistency is the last refuge of the unimaginative."
-- Oscar Wilde,
"The Relation of Dress to Art," Pall Mall Gazette (Feb. 28, 1885)
1 Another example is attack ads. It drives me mildly crazy to see an old out of context quote from a rival politician played over and over as if that actually means something. It's such a blatant insult to the viewer's intelligence, it makes me want to avoid voting for any party that runs attack ads, but that could mean not voting at all.