Italy's anti-establishment and anti-euro party Five Star Movement (5SM) represent the greatest threat to euro area stability, analysts told CNBC on Tuesday, as the populist party surged ahead of its political rivals in the latest opinion poll, putting it on course to be the biggest party if elections were called. 5SM leader Beppe Grillo has enjoyed a recent, and remarkable, uptick in support, buoyed in part by the divisions in the ruling Democratic Party (PD) as former Prime Minister Matteo Renzi attempts to regain support. Grillo, who has campaigned for Italy to hold a referendum on the single currency if...