The shocking murder of British parliament member Jo Cox and the Orlando shootings were both hate crimes that defy political labels, whatever the professed motives of the killers. Nobody can predict what will set off a deranged killer and it would be deplorable to tar legitimate political campaigns because a killer identified with one cause or another.

But it's impossible to deny that these killings have the power to affect both the vote on Britain's proposed exit from the European Union and the U.S. presidential election. Violence is not just morally repugnant, it is uncomfortable. In most societies, people default to safety and order.

On May 6, 2002, Volkert van der Graaf, an animal rights activist, shot Pim Fortuyn, the leader of a Dutch populist, anti-immigrant party competing in that year's parliamentary election, scheduled for May 15. The campaigns fell silent in shock: The Netherlands had a tradition of consensual politics, and violence wasn't part of the political culture. Yet the election was not canceled (as the Brexit vote shouldn't be, either: re-arguing the issue at some later date wouldn't do anyone any good).