Some of it is calculated:
https://twitter.com/jetpack/status/558468003315335169
But some of it is subconscious, as Eric Posner explains:
To investigate the role of motivated reasoning in the sort of institutional flip-flops that politicians and judges engage in, Harvard Law School professor Cass Sunstein and I conducted a series of surveys. In one, we asked people whether President Bush acted rightly by using a loophole to make appointments in defiance of Senate opposition.
Most Republicans said he did the right thing while most Democrats said he acted wrongly. We then put Obama’s name in for Bush with a different group of respondents and asked the same question. This time the vast majority of Republicans opposed the appointments while most Democrats said he did the right thing.
We posed a similar question about use of the signing statement—Bush’s and now Obama’s controversial practice of signing a bill while stating that he will not enforce portions of it. Again, Republicans were more sympathetic to the practice when the question invoked Bush, Democrats when the question invoked Obama.
Like the football fans, most partisans see a neutral process in a favorable light if it advances their parties’ goals and in an unfavorable light if it does not. And this is true even if partisanship is not salient. We asked another group of respondents whether they supported same-sex marriage and whether they thought Congress could either mandate nationwide recognition of same-sex marriage or prohibit states from recognizing same-sex marriage. Same-sex marriage supporters were much more likely to believe that Congress could mandate it than ban it; opponents believed the opposite.
We call this phenomenon “merits bias”—a bias in favor of evaluating a rule or institution in terms of whether it advances one’s political goals. We suspect that some politicians and even judges suffer from merits bias while others cynically exploit merits bias in the general public. Many Democrats really do believe that the filibuster is justified when it blocks Republican nominees and not when it blocks Democratic nominees. And the same with Republicans. Political operatives and sophisticated observers know it’s a game, but most people don’t.
The Dish 