Cindy and their family.
"Senator John Sidney McCain III died at 4:28pm on August 25, 2018", a statement from McCain's office reads.
McCain had not been seen in Washington since last Decmeber, and spent his last few months at home in Arizona. After gambling on political neophyte Sarah Palin as his vice presidential running mate, McCain lost in 2008 to Democrat Barack Obama, who became the first black USA president.
McCain was edged out by George W. Bush for the Republican presidential nomination in 2000, but became his party's White House candidate eight years later. Obama says despite their differences, they shared a "fidelity to something higher - the ideals for which generations of Americans and immigrants alike have fought, marched, and sacrificed".
"I was with my father at his end, as he was with me at my beginning", said his daughter, Meghan McCain. McCain had been a rare and outspoken Republican critic of Trump, accusing him of "naivete", "egotism" and of sympathizing with autocrats.
Now that the trio is missing its driving force, Graham wrote that "America and Freedom have lost one of her greatest champions".
"And to me, he was a friend whom I'll deeply miss".
McCain, 81, was diagnosed with an aggressive brain tumour, called a glioblastoma, in July a year ago, and chose to stop treatment on Friday. Before joining the upper chamber, he served as a U.S. representative from 1983 to 1987.
The family of the six-term US senator announced on Friday that he had made a decision to end treatment in his battle against brain cancer, which he had fought against for over a year.