Say what you will about President Donald Trump’s hiring of financier Anthony Scaramucci as White House communications director, but it’s a damn good troll.

The appointment — which caused press secretary Sean Spicer to resign and sparked vehement opposition from Chief of Staff Reince Priebus and chief strategist Steve Bannon — came, according to Politico, after Trump grew “enamored with Scaramucci since he managed to get a retraction from CNN on a story published in late June about his alleged Russia connections.”

In other words, Trump made a big appointment that alienated many top members of his administration for the grand purpose of … telling CNN to suck it.

It’s a strange way to do business, but aggressively sticking it to perceived political enemies has become a key part of Trump’s PR strategy as president. In a recent interview with the New York Times, Trump took multiple opportunities to attack Hillary Clinton, months after defeating her in the presidential election. “Hillary Clinton was dying to get back with Russia [as secretary of state],” he interjected at one point. “Her husband made a speech, got half a million bucks while she was secretary of state. She did the uranium deal, which is a horrible thing, while she was secretary of state, and got a lot of money.”

“There wasn’t much I could say about Hillary Clinton that was worse than what I was already saying,” he summed up.

This is weird. Barack Obama didn’t spend 2009 giving newspaper interviews in which he repeatedly dunked on McCain. He didn’t spend 2013 dunking on Mitt Romney, and George W. Bush didn’t spend 2005 dunking on John Kerry or 2001 dunking on Al Gore.

But Trump has devoted much of his early president to partisan attacks that serve little near-term purpose, other than sticking it to the libs:

The Republicans never discuss how good their healthcare bill is, & it will get even better at lunchtime.The Dems scream death as OCare dies! — Donald J. Trump (@realDonaldTrump) July 19, 2017

Hillary Clinton colluded with the Democratic Party in order to beat Crazy Bernie Sanders. Is she allowed to so collude? Unfair to Bernie! — Donald J. Trump (@realDonaldTrump) June 25, 2017

The media has not reported that the National Debt in my first month went down by $12 billion vs a $200 billion increase in Obama first mo. — Donald J. Trump (@realDonaldTrump) February 25, 2017

Why isn't the House Intelligence Committee looking into the Bill & Hillary deal that allowed big Uranium to go to Russia, Russian speech.... — Donald J. Trump (@realDonaldTrump) March 28, 2017

To some extent, this is basic political messaging. Trump is getting attacked for his floundering health care bill, so he changes the subject to how humiliated Democrats are going to be when a bill is finally passed. He’s getting attacked for his campaign’s alleged collusion with the Russian government, so he brings up irrelevant allegations about Hillary Clinton’s primary campaign and a State Department-approved Russian company’s purchase of a mining company. He feels like he needs better defense, so he hires Scaramucci, who’s been an effective cable TV surrogate.

But in a way, it’s reflective of Trump’s overall political strategy, and why he’s been able to attract a rabid base of followers that has stuck with him through every setback and scandal.

Trump has appointed mostly traditional conservatives to staff his administration, which has led to predictably conservative policy: conservative budgets, conservative regulatory rollbacks, conservative Supreme Court and other judicial appointments. In his own comments, however, Trump has been vaguer. He’s called both for sweeping tax cuts and for tax hikes on the rich. He’s promised to protect Medicaid and then embraced bills that would cut it. He alternately embraced conservative health plans and promised to “cover everybody.”

Why would any voters be loyal to somebody whose beliefs they can’t nail down? The reason, basically, is Trump’s dunks on Hillary, his troll hires like Scaramucci. It’s negative partisanship: partisan identity motivated less by attachment to a given set of beliefs than by hatred and fear directed at a political out-group.

The rise of negative partisanship

A common understanding of how politics works is that voters have some beliefs about how government should work, they identify candidates who share those beliefs, and then they vote for those candidates. Elected institutions like Congress and the presidency thus reflect the aggregated wishes and desires of the people. This is what political scientists Christopher Achen and Larry Bartels have called the “folk theory of democracy.”

The problem is that the folk theory is totally wrong. The vast majority of people don’t sort themselves into political groupings based on firmly held beliefs. Most people don’t have firmly held beliefs about political issues at all, and most people aren’t and don’t want to be deeply involved in politics. When people do express political opinions, they’re typically copying the beliefs of elites such as elected officials, rather than the other way around.

And for people who do follow and want to be involved with politics, participation has started to take the form of fandom rather than deep engagement in local parties and organizing. Tufts political scientist Eitan Hersh calls this “political hobbyism.” "Public spiritedness can take a back seat to partisanship when politics is treated as a game," he warns.

And indeed, that’s what we’ve seen in recent decades. Political scientists and pollsters have increasingly noticed that partisanship in the modern era is driven less by loyalty to a given political program and more by animosity toward one’s political enemies. "Partisan affect is inconsistently related to policy preferences," political scientists Shanto Iyengar, Gaurav Sood, and Yphtach Lelkes wrote in a 2012 paper.

But "the mere act of identifying with a political party is sufficient to trigger negative evaluations of the opposition, and exposure to prolonged media-based campaigns only reinforces these predispositions. … Democrats and Republicans not only increasingly dislike the opposing party, but also impute negative traits to the rank-and-file of the out party."

In other words, being a Democrat might mean that you support Democratic policies, but it definitely means you don’t like Republicans.

Iyengar, Sood, and Lelkes find that the share of Democrats and Republicans saying they would be upset if their child married someone of the opposing party has dramatically increased from 1960 to 2010. Members of both parties were likely to characterize the opposition as less intelligent and more selfish than members of their own party.

The Pew Research Center's polling concurs. "Partisans’ views of the opposing party are now more negative than at any point in nearly a quarter of a century," a 2016 report declared. "For the first time in surveys dating to 1992, majorities in both parties express not just unfavorable but very unfavorable views of the other party. And today, sizable shares of both Democrats and Republicans say the other party stirs feelings of not just frustration, but fear and anger."

Perhaps most remarkably, when asked why they were members of their parties, Republicans were more likely to cite a belief that Democratic policies would be bad for the country than a belief that Republican policies would be good. For Democrats, nearly as many cited opposition to Republican policies as support for Democratic ones.

A more recent 2017 poll by Pew found that 59 percent of Americans say it's "stressful and frustrating" to talk to people with different opinions about Trump; among Democrats, the share is 68 percent. Thirty-five percent of Democrats (19 percent of Americans) said that if a friend voted for Trump, it would put strain on their friendship.

Political scientists Alan Abramowitz and Steven Webster have named this phenomenon “negative partisanship,” and it's an extremely powerful explanation for why American politics looks the way it does. It helps explain why people maintain strong partisan identities even when most voters don’t hold much in the way of firm political beliefs. They have a tribal commitment to their team, but much more powerfully have a fear of the opposing team.

And negative partisanship can help us make sense of Trump’s bizarre staffing choices, and his insistence on continuing to attack Hillary Clinton and other Democratic enemies, long after they’ve ceased to pose a real political threat to him. Trump’s supporters are as susceptible to this kind of tribal politics as everybody else. And by attacking Clinton and other Democratic hate figures (as well as his other perpetual target, the media), Trump is able to capitalize on his supporters’ strong negative feelings toward them, feelings which are likely stronger than any loyalty to a specific political program.

Trolling enemies on Twitter may look immature. Appointing Scaramucci might seem bizarre. But it could also be what Trump’s supporters want.