One part of life where [American] restlessness does not apply is politics. Almost everyone who voted for Donald Trump in 2016 had voted for Mitt Romney four years earlier, just as almost everyone who voted for Hillary Clinton had previously voted for Barack Obama. People who vote tend to settle on a party with which they identify in young adulthood, then stick with it. By contrast, half of American adults have switched religious denomination at some point, according to the Pew Research Centre. The datasets do not line up in a way that makes the conjecture possible to prove, but it is a fair bet that, at least among those most engaged in politics, Americans are more likely to change their religion than to change their party.

Partisanship eats away at the sense that it is possible to think for yourself. Partisanship also obviates the need to take opposing views seriously. Faced with a political decision, such as whether to support Brett Kavanaugh’s nomination, or talks between America’s government and North Korea’s, it is far easier to listen to the people you normally agree with and adopt their view. Weighing up evidence is hard, time-consuming work: in this respect, partisan thinking is another shortcut to happiness.

When thinking is so entrenched, those who change their minds have a kind of superpower, for only they can demonstrate independent reasoning. That explains the fascination with the small subgroup of voters who chose Obama in 2012 and then Trump in 2016. Psephologists and journalists treat these creatures as ancient Romans treated birds, studying their flight paths to see what the omens are. Writers who have switched sides, though less numerous, exert a similar fascination.

https://www.economist.com/united-states/2018/10/20/switching-parties-in-trumps-america