SOFIA, Nov 6 (APP/AFP): Bulgarians were voting Sunday in a first round of a presidential election, a key test of Prime Minister Boyko Borisov’s popularity that could also determine relations between the EU’s poorest country and Russia. If his candidate and protegee Tsetska Tsacheva fails to win the presidency, Borisov might call early legislative elections, plunging Bulgaria into renewed political uncertainty, experts say. Opinion polls suggest that Tsacheva, currently speaker of parliament, will top the crowded field of 21 candidates with around 30 percent of the vote. But close on the 58-year-old’s tail will be MiG ace and former air force head Rumen Radev, the candidate of the opposition Socialists who is seen as more sympathetic to Russia.