U.S. presidential candidate Donald Trump canceled a campaign rally Friday night amid security concerns just hours after the Republican front-runner earned the endorsement of a former rival who said the billionaire's pugnacious campaign style is belied by a more thoughtful, private side.
（来源：Reuters）
1. U.S. presidential candidate Donald Trump是句子的主语， Donald Trump是U.S. presidential candidate的同位语。candidate为名词，意思为：候选人。
5. Republican front-runner 意思为共和党总统竞选人领先者。front-runner是政治术语，意思是某人（偶尔指某集团，组织）指在选举中的位列第一。《大西洋月刊》（The Atlantic）曾刊登过一篇文章，名为The Front-Runner Fallacy（领先者的假象），大家有兴趣看看。
6. earn the endorsement of ... 取得某人的支持。earn的词条和搭配，考生务必要弄清楚，该词用法简单，但是往往一不留神，就理解错误或翻译错误。endorsement是动词endorse的名词形式，endorse本意为在支票背面签名，中文称之为背书。学过财务或会计等商科类的同学应该了解，支票在转让的过程中有一种是转让支票出去的人要在支票背后签名（或盖章），即背书，背书的人就会对这张支票负某种程度、类似担保的偿还责任，换个角度来看，背书的人愿意为此担当一定的责任与风险，因此，无论是中文的“背书”还是英文的”endorse“，都引申出”担保、保证“的意思，即为别人的事情或为别人说的话作担保、保证。久而久之，这个词也可以指支持或赞成某人的言论，行为等等，而且语气相当正式，暗含背书人并不是随便说说而已。
a former rival 意思为之前的对手。根据后文：
"There are two different Donald Trumps: there's the one you see on the stage and there's the one who's very cerebral（清醒的；凭理智行事的）, sits there and considers things very carefully," Ben Carson said Friday as he became the second former Republican candidate to back Trump in the White House race.
所以这个former rival指的就是美国传奇的神外科医生，美国前20大名医Ben Carson（本·卡森），常常去丁香园转的童鞋一个对他不陌生，他是世界上首位成功给脑部连体婴儿实施分离手术的外科医生，也是2016年美国总统大选共和党竞选人中唯一的非裔。 在3月4日，这位民调支持率一度排名首位的传奇医生正式宣布退出竞选美国总统，因为他看到自己在竞选中“没有了前進的道路”。。他也是继首位支持川普的现任美国州长-美国新泽西州州长、共和党人克里斯·克里斯蒂之后，第二名支持特朗普的党内参选人（as he became the second former Republican candidate to back Trump in the White House race.）
本·卡森一直被人诟病其政治经验不足本·卡森一直被人诟病其政治经验不足
7. who said the billionaire's pugnacious campaign style is belied by a more thoughtful, private side.这是由关系代词who引导定语从句，在从句中做主语，从句修饰a former rival.
said后有一个省去了引导词that的宾语从句，援引出这位前对手的话语。the billionaire当然就指川普了，并且他是土豪。形容词pugnacious超纲单词，意思为very eager to argue or fight with people 好斗的，好战的；campaign style意思为竞选活动中表现出来的风格。川普在此次竞选活动中的种种”任性“”失控“”狂妄“的表情，用川普式竞选风格来概括pugnacious campaign style最适合不过了。
8. belie在宾语从句中是被动态，belie意思为”与…不符；掩饰“。被上面掩盖？by引出：a more thoughtful, private side 考虑更为周到，更为人所不知的一面。结合刚刚援引的原文，就可以理解本卡森指的是真实的川普与在大众媒体面前的川普并不一样。
"There are two different Donald Trumps: there's the one you see on the stage and there's the one who's very cerebral（清醒的；凭理智行事的）, sits there and considers things very carefully," Ben Carson said Friday as he became the second former Republican candidate to back Trump in the White House race.
原文中还有一段可以有助于理解：
The soft-spoken retired neurosurgeon, who dropped out of the race last week, said the American people would be "comforted" when they discover Trump's gentler side.
The soft-spoken retired neurosurgeon 指的就是本卡森了，who引导的非限制性定语从句指出其已在上周退选；后面用宾语从句引出本卡森的话语，本卡森说，当发现到川普”温和“的一面时，人们会感到安心点。