I completely disagree that partisanship has increased recently in US politics.
For those engaged in them, the fights over politics have been bitter, deep-seated, and ongoing since the founding of the Republic (ask Alexander Hamilton!).
The difference is that until the mid- to late-80s, politics remained an insider sport. Even as late as the first Reagan administration, 'government' was the exclusive province of long-term politicians, covered by reporters of a very limited number of news services, who were equally-long-serving.
Suddenly in the 80s there was 'talk radio' - a commercial response to the public's long-perceived leftish bias in corporate media systems - actively prying into the minutiae of the daily affairs of Washington. A careful minuet of positions, negotiations, and alliances-of-convenience was disrupted by the blundering commentary of ill-informed entertainers posing as journalists, cheerfully inciting voter outrage by simplistic commentary on complicated and subtle issues. Professional media organizations, with their instinctive defensiveness, only reinforced the 'outsider', and 'underdog' position of the talk-radio circuit
Certainly any democracy has a certain amount of grandstanding; nevertheless national government was historically an ongoing process of backroom deals, tit for tat, and compensatory back-scratching....no longer. Never mind that compromise is the life blood of governance.
Later, the internet's ability to allow anyone to take the position of these talk-radio hosts - to "tell a story" unfiltered to tens of millions of people within moments, now coupled with a public whose general educational level is lower than ever means that for the political class - for whom maintaining their public image and position is always uppermost - is almost forced to become more strident, more aggressive, and more reactionary to inoculate themselves against whatever might leak out.
Some degree of transparency is essential to good governance. The brilliance of the US Constitution is that it ASSUMES politicians are scoundrels and will be self-interested. But naked democracy is NOT constructive; not everyone can bear watching sausage be made. And yes, I'm asserting that the general public is too uninformed and too distracted by daily life to make well-reasoned judgments on nuances of public policy.
The 24/7 news media makes every piece of trivia an issue.
The internet practically makes every issue a public plebiscite.
And we're surprised that demagogues control our public discourse? Really?