TEGUCIGALPA, Nov 30 (Reuters) - The ruling National Party of Honduras is conceding defeat in Sunday"s presidential elections, a senior party figure said on Tuesday, leaving leftist candidate Xiomara Castro poised to become Honduras" first female leader. Kilvett Zabdiel Bertrand, executive secretary of the National Party, told Radio America that its presidential candidate Nasry Asfura will soon hold a news conference to confirm the party"s 12-year stint in power is ending. "We tell the National Party base with our heads held high that we are going to create an opposition government," Bertrand told Radio America. Castro has racked up a lead of almost 20 percentage points over Asfura. With just over 52% of votes counted on Tuesday afternoon, Castro had 53.5% support, and Asfura 34%. The formal concession will bring to an end a turbulent period under the conservative National Party, which has been dogged by scandals and corruption accusations, especially during the two terms of outgoing President Juan Orlando Hernandez. Hernandez is deeply unpopular and has been implicated in a drug trafficking case in a U.S. federal court. He denies wrongdoing, but could face an indictment when he leaves office. Castro"s victory will see the left return to power after a 12-year hiatus that followed the ousting of her husband, former President Manuel Zelaya, in a coup in 2009. Castro has already hailed a "resounding victory in the whole country" and her supporters danced, cheered and waved flags in anticipation of Hernandez"s departure. Castro faces big challenges in Honduras, where joblessness, crime, corruption and the threat of transnational drug gangs has helped spur record migration to the United States. She managed a strong showing in Sunday"s election despite findings by the European Union vote observer mission that the National Party had used state resources to boost its campaign. The smooth transmission of early election results had aided transparency and confidence, the EU mission said. But it criticized pre-election political violence and "abuse of state resources", such as a rise in handing out of welfare vouchers. "The state media visibly favored the ruling party and its presidential candidate," said the mission"s head, Željana Zovko. Over the last 24 hours there was also a lengthy hold up in vote counting that stoked suspense across the country. The delay in the count stirred up memories of the 2017 election, when the opposition candidate"s lead suddenly began to evaporate after the electoral council restarted the tally following a lengthy suspension. That interruption gave rise to accusations of fraud and deadly protests, but there has been no unrest so far this time, with voters reassured by Castro"s much bigger lead. Castro"s team is already preparing for government. Hugo Noe, head of the campaign"s policy platform, told Reuters she will seek to negotiate a new debt deal with the International Monetary Fund when she takes office in January. read more