The assassination attempt on Robert Fico, Slovakia’s prime minister, is unprecedented in the country’s history.  But the attack, which the premier is likely to survive, speaks to an increasingly poisonous atmosphere in the central European nation of 5.5 million people. In response to the attack, Zuzana Caputova, the country’s liberal outgoing president, and her successor Peter Pellegrini, an ally of the prime minister, have jointly called for calm.  But some sense...