Senator John Cornyn lost his election Wednesday to become the next Senate majority leader to Senator John Thune, of South Dakota, ending a years-long effort to lead his party conference.Senator Mitch McConnell, of Kentucky, announced this year that he would not seek another term leading the party, ending his seventeen-year tenure. He is the longest-serving party leader in the history of the U.S. Senate. The opening led to the first competitive, open campaign for GOP leader in decades, the stakes of which were raised after Republicans won control of the upper chamber last week.Cornyn had spent decades climbing the ranks of the Senate GOP, building relationships and raising money that would be crucial in the vote. But those proved insufficient in wooing a majority of…