These days, politics is about what you hate as much as what you like

(CNN)Ask people why they belong to their political party and they're almost as likely to tell you it's because the other party is so bad as they are to tell you they like something about the party they joined.

The trend is even more evident among independents. Republican and Democratic independent leaners will tell you that the harm of the opposing party's policies is the major reason they're leaning toward one party.
Americans don't like other parties so much that it's become core to their political identity.
These are the results of a recent poll by the Pew Research Center, which confirm the continuation of a several decades-long trend in political attitudes by partisans against each other.
    The top "major reason" both Republicans (76%) and Democrats (72%) identify with their respective parties is that they think their own party's policies are good for the country.
    But a close second "major reason" both Republicans (71%) and Democrats (63%) identify the way they do is that the other party's policies are harmful, according to the Pew survey.
    For years, Americans have been getting more intensely distrustful and negatively biased against members of the opposing parties.
    The presence of this antipathy is slightly stronger among Republicans -- and has ticked up recently -- but it is still very strong among Democrats. Seventy-one percent of Republicans say a major reason for identifying with their party is that Democratic policies are harmful to the country. That's up from 68% from when the same question was asked in spring 2016.
    Sixty-three percent of Democrats say that the other party's policies being harmful to the country is why they identify as Democrats. That's up just 1 percent, from 62% in 2016.
    This is not an unfamiliar phenomenon. Political scientists and pundits were tied into knots trying to explain why white voters without a college degree were drawn to Trump.
    There's a sizable pile of evidence holding up those explanations. But parties have been changing in ways that go well beyond Trump.
    The parties themselves have become much more ideologically cohesive, much less likely to be composed of ideological diversity or dissent. Those who tune into party leadership and take in partisan information are much more likely to have negative feelings about the policies of other parties and to even ignore the reality of basic facts. In tests of subconscious association, hostile feelings are elicited by partisanship are comparable -- or even stronger than -- those elicited by race.
    There are many explanations given for why parties have become this way -- from geographic and ideological sorting to cable news to the motivating power of enemies -- but for now, one group is taking advantage of it: political elites and leadership. "We got elected on Drain the Swamp, Lock Her Up, Build a Wall," former White House chief strategist Steve Bannon told Bloomberg. "This was pure anger. Anger and fear is what gets people to the polls."