Republican presidential contenders hold their first debate Thursday in Cleveland, the first major event in what promises to be a long and hard-fought battle for the party's 2016 presidential nomination. VOA national correspondent Jim Malone has a preview from Washington: ________________________________________________________________________ 共和党总统候选人周四在克利夫兰举行首场竞选辩论,这是竞选2016年总统提名的第一场重大较量,竞选之路势必为一场漫长持久的硬仗.VOA国家记者杰姆马伦从华盛顿报道: _______________________________________________________________