WASHINGTON (Reuters) - U.S. Senator Bernie Sanders leads in the latest poll of Iowa voters released on Friday and conducted by the state’s largest newspaper, one of the most watched surveys in the state, which holds the first presidential primary contest next month. Sanders received 20% in the poll, which was released by The Des Moines Register and conducted by Selzer & Co, an Iowa polling firm. The poll found a clear top tier of four candidates competing in Iowa.