SOFIA, Oct 1 (Reuters) - Bulgaria"s centre-right GERB party on Friday endorsed a university rector to run for president in a contest to be held in tandem with a parliamentary election aimed at building a working government and ending months of political uncertainty. GERB said it backed Sofia University Rector Atanas Gerdzhikov, 58, a professor in Ancient and Medieval Literature who has run Bulgaria"s most renowned university since 2015, to challenge incumbent Rumen Radev, 58, for the presidency, a largely ceremonial position. "Prof. Gerdzhikov is a man who can unite the nation," GERB"s leader, former premier Boyko Borissov told reporters. "We were happy to hear he will be nominated by an independent committee and we decided to support him." The parliamentary election will be the country"s third this year, following inconclusive votes in April and July that failed to produce a government amid wrangling and rivalry among Borissov"s opponents. read more Borissov, a harsh critic of Radev, has accused the former airforce commander of stoking deep divisions in society by openly supporting massive anti-corruption protests against Borissov"s centre-right administration in 2020. Popular anger against widespread corruption in the European Union"s poorest member state put an end to almost a decade of political dominance by Borissov, who stood down in April after his party had ruled for most of the past decade. Radev, who has maintained high approval ratings since he was elected in 2016, is supported by Borissov"s political opponents - the Socialists, the anti-establishment ITN party and a newly formed centrist party, We Are Continuing the Change. read more