Republican Senator Susan Collins, of Maine: "I will not be voting for Donald Trump for president."

http://www.cnn.com/2016/08/08/politics/susan-collins-donald-trump-republican-party-oped/index.html

Here is the essay Senator Collins wrote for The Washington Post:  https://www.washingtonpost.com/opinions/gop-senator-why-i-cannot-support-trump/2016/08/08/821095be-5d7e-11e6-9d2f-b1a3564181a1_story.html