Turkey's Erdogan, main rival stage final election rallies

By Ezgi Erkoyun and Ali KucukgocmenISTANBUL (Reuters) - President Tayyip Erdogan and his main challenger, Muharrem Ince, made a final push for support at rival rallies in Istanbul on Saturday, a day before presidential and parliamentary elections widely viewed as the most crucial in Turkey for decades.The winner of Sunday's presidential contest will acquire sweeping new executive powers under a constitutional overhaul backed by Erdogan and endorsed last year by a narrow majority of Turks in a re