Former Democratic president Bill Clinton and his wife Hillary wished him a swift recovery, with this year’s presidential contender saying McCain "is as tough as they come."
Vice President Mike Pence also extended his prayers for the fellow Republican. "Cancer picked on the wrong guy. John McCain is a fighter and he'll win this fight too. God bless!" he wrote.
McCain’s family said in a statement they were reviewing treatment options, which may include a combination of chemotherapy and radiation. His daughter Meghan also suggested this was not the first time the 80-year-old was diagnosed with cancer.