SOFIA (Reuters) - Bulgaria's incumbent President Rumen Radev is seen winning the decisive round of Sunday's presidential election by a large margin after voters backed his strong anti-corruption message, exit polls by Alpha Research and Gallup International showed.

       Radev, supported by several anti-graft parties and the Socialists, won 64-66% of the vote, compared with 32-33% for Anastas Gerdzhikov, backed by the centre-right GERB party of former premier Boyko Borissov, according to the exit polls.

       (Reporting by Tsvetelia Tsolova, Editing by William Maclean)