U.S. Senate investigators sought and received materials from the estate of Peter W. Smith, a longtime Republican operative who reportedly acknowledged shortly before his death that he spearheaded an effort to obtain missing Hillary Clinton emails from Russian hackers, two sources familiar with the matter told ABC News. Smith, a private-equity executive from Chicago who had been active in Republican politics, died at age 81 on May 14. Ten days earlier, he told a reporter from the Wall Street Journal that he had led a robust bid during the early months of the 2016 presidential contest to find what he...