Slovenia’s populist opposition has mounted a campaign against “degenerate” artists as it seeks to topple government plans for special pension top-ups for award-winning artists in a referendum on Sunday. Voters in the central European country will cast their verdict on a government bill that details the conditions and terms under which certain artists can claim an allowance to be added to their pensions. For the referendum law to be rejected, at least one-fifth of all eligible voters among Slovenia’s population of 2.12 million must vote “no”. The number of “no” votes must also represent more than half of all votes...