McCain, a fighter pilot during the Vietnam War, was shot down in 1967. He spent five subsequent years in prison camps while being subjected to torture, according to an Almanac of American Politics profile of the senator. 

The 77-year old McCain has blasted Cruz for comparing GOP pundits opposing his effort to people during WWII who said the Nazis could not be defeated. He has long opposed Cruz's tactic, and says it is prone to defeat. 

Nonetheless, McCain said he enjoyed a dinner with Cruz a few weeks back and admires the freshman senator. 

Cruz finished a 21-hour and 19-minute speech on the Senate floor Wednesday morning in opposition to a Democratic plan to strip defunding of ObamaCare language from a continuing resolution to fund the government.