星期四，美国共和党剩下的4位总统参选人在密西根州举行一场辩论会。居于领先地位的川普刚赢得了一批州的初选，势头强劲，但也面临新的阻力。
60名共和党外交政策资深人士星期三晚间发表了一封反对川普竞选的联署公开信，表示川普的行为方式将“使美国变得更不安全，而且将削弱美国在世界上的地位”。信中列举了一系列反对川普竞选的理由，包括川普发表反穆斯林言论、支持使用酷刑、主张进行贸易战以及认为墨西哥应在美墨边界修筑一道高墙。
信件的签署者包括前美国国土安全部部长切尔托夫、曾担任美国国务院副国务卿的前世界银行总裁佐利克以及前五角大楼高层官员扎克海姆。
与此同时，3个美国民间组织也计划花费巨额资金，制作抨击川普的广告。
The four remaining Republicans in the presidential race hold a debate Thursday in Michigan with frontrunner Donald Trump carrying momentum from another batch of state wins but facing new efforts to halt his campaign.
A group of 60 Republican foreign policy veterans signed a joint letter released late Wednesday opposing Trump, saying he would “act in ways that make America less safe, and which would diminish our standing in the world.” It lists a number of objections, including anti-Muslim rhetoric, a support for the use of torture, advocating trade wars and insisting Mexico will build a border wall.
The list of signatories includes former U.S. Homeland Security Secretary Michael Chertoff, former World Bank President and Deputy Secretary of State Robert Zoellick and former top Pentagon official Dov Zakheim.
Meanwhile, three outside are planning to spend millions of dollars in new ads attacking Trump.