An aide adjusts a microphone on U.S. Senator John McCain (R-AZ) as he prepares to announce that he will seek re-election for his seat during a speech to the Arizona Chamber of Commerce and Industry in Phoenix, Arizona April 7, 2015. McCain of Arizona, who was the Republican presidential nominee in 2008, said on Tuesday he will seek a sixth term in office in 2016. He was accompanied by his wife, Cindy McCain (R). REUTERS/Nancy Wiechec