When President Obama was contemplating missile strikes in Syria four years ago, in the aftermath of a deadly chemical weapons attack, very few people thought it was a good idea. Just 38 percent of Democrats and a bare 22 percent of Republicans supported the idea.

Today, most Democrats are similarly apprehensive. Only 37 percent back President Trump’s weekend bombing campaign. Republicans, by contrast, have had a near-total change of heart. The same Washington Post-ABC News poll finds that 86 percent of Republicans support the strikes, suggesting that a huge number of them based their decision on the proxy of who happened to be president at the time.

Negative partisanship—the observable effect that antipathy to the other party has on public opinion—seems, like everything else in U.S. politics, to be asymmetric between the parties. Republicans are the key drivers of it.

We can see the asymmetry at work in other realms, too. Immediately after the election, Democrats’ views of economic conditions (the current state of the economy and the outlook) fell modestly but abruptly from +26 to +17. That effect was overwhelmed by Republicans, whose views of the economy shot up 16 points.

Pew has observed the same phenomenon: