McCain underwent a minimally invasive craniotomy at Mayo Clinic Hospital in Phoenix, Arizona, on July 14, 2017, in order to remove a blood clot above his left eye. His absence prompted Senate Majority Leader Mitch McConnell to delay a vote on the Better Care Reconciliation Act.
Five days later, Mayo Clinic doctors announced that the laboratory results from the surgery confirmed the presence of a glioblastoma, which is a very aggressive brain tumor. Standard treatment options for this tumor include chemotherapy and radiation, although even with treatment, average survival time is approximately 14 months. McCain was a survivor of previous cancers, including melanoma.
President Trump made a public statement wishing Senator McCain well, as did many others, including former President Obama. On July 19, McCain's senatorial office issued a statement that he "appreciates the outpouring of support he has received over the last few days. He is in good spirits as he continues to recover at home with his family in Arizona. He is grateful to the doctors and staff at Mayo Clinic for their outstanding care, and is confident that any future treatment will be effective." On July 24, McCain announced via Twitter that he would return to the United States Senate the following day.
McCain's family announced on August 24, 2018, that he would no longer receive treatment for his cancer. The next day, at 16:28 MST (23:28 UTC), he died with his wife and family beside him at his home in Cornville, Arizona, four days shy of his 82nd birthday. He will lie in state at the U.S. Capitol Rotunda.
Tributes were widely given on social media, although not universally favorable, including from Congressional colleagues, former Presidents Jimmy Carter, George H.W. Bush, Bill Clinton, George W. Bush, Barack Obama, and President Donald Trump and Vice President Mike Pence. Republic of China (Taiwan) President Tsai Ing-wen, Israeli Prime Minister Benjamin Netanyahu, Canadian Prime Minister Justin Trudeau and former Prime Minister Stephen Harper, former Australian Prime Minister Malcolm Turnbull, German foreign minister Heiko Maas, Pakistani foreign minister Shah Mahmood Qureshi, and former Vietnamese ambassador to Washington Nguyen Quoc Cuong, also sent condolences.
Arizona Governor Doug Ducey will appoint McCain's interim replacement until a special election is held in 2020, the winner of which will serve to the end of McCain's term in January 2023. Under Arizona law, the appointed replacement must be of the same party as McCain, a Republican. The potential appointees include McCain's widow Cindy, former Senator Jon Kyl, and former Representatives Matt Salmon and John Shadegg.