US Senator John McCain, a prisoner of war in Vietnam and a two-time contender for the presidency, died on Saturday at his home in Arizona at the age of 81.
McCain had been diagnosed with a malignant brain tumor, called a glioblastoma, in 2017 and was being treated periodically with radiation and chemotherapy.
According to a statement from his office, McCain died at 4:28 p.m. local time. His family had announced this week that he was discontinuing medical treatment.
The son and grandson of four-star admirals, McCain endured more than five years of imprisonment and torture by the North Vietnamese as a young naval officer.
"My heart is broken. I am so lucky to have lived the adventure of loving this incredible man for 38 years. He passed the way he lived, on his own terms, surrounded by the people he loved, in the the place he loved best," McCain's wife Cindy McCain said in a post on Twitter.
Condolence messages poured in from across party lines on McCain's passing. US President Donald Trump tweeted, "My deepest sympathies and respect go out to the family of Senator John McCain. Our hearts and prayers are with you!".
Former US President Barack Obama said in a statement that while McCain and he came from completely different backgrounds and competed at the highest level of politics, "we shared, for all our differences, a fidelity to something higher - the ideals for which generations of Americans and immigrants alike have fought, marched and sacrificed."
Bush called his one-time political rival "man of deep conviction and a patriot of the highest order" and a "friend whom I'll deeply miss."
Former vice president Al Gore said he always admired how the senator "would work to find common ground, no matter how hard."
McCain was close friends with Senator Lindsey Graham and former senator Joe Lieberman -- a trio dubbed the "Three Amigos."
"The demand for our leadership in the world has never been greater. People don't want less of America they want more," McCain said in 2012. "Everywhere I go in the world, people tell me that they still have faith in America. What they want to know is whether we still have faith in ourselves."