T HE CHEERS at Rafal Trzaskowski’s election party on May 18th sounded unconvincing. So was his margin of victory. The liberal mayor of Warsaw came away with 31.4% of the vote in the first round of Poland’s presidential election,

Since winning power back from the hands of his populist rivals a year and a half ago, Poland’s Prime Minister Donald Tusk has faced one very stubborn roadblock to his plans: the country’s president.