"My heart aches for Cindy, Meghan, and the rest of the McCain family", said Sen. The statement also says he served the US faithfully for 60 years. "He loved me, and I loved him", she wrote.
Upon hearing of McCain's death, Obama released a statement: "John McCain and I were members of different generations, came from completely different backgrounds, and competed at the highest level of politics".
First Lady Melania Trump also expressed her condolences and thanked the Senator for his "service to the nation".
President Barack Obama, who ran against McCain for the presidency in 2008, said that Americans remain in the former senator's debt because of all that he did for the country.
He added: "But all of us can aspire to the course to put the greater good above our own". A friendship struck between John McCain, the former POW, and John Kerry, the former anti-war protester, helped lead to America's restoring relations with Vietnam, where US involvement in the war ended up tearing apart our own country.
When Trump announced his candidacy for the Republican presidential nomination in June 2015, suggesting that many Mexican immigrants were criminals and "rapists", McCain denounced him for using language that "fired up the crazies". Bush said. "Some voices are so vibrant, it is hard to think of them stilled".
Former President George W Bush described McCain, his one-time political rival, as a "man of deep conviction and a patriot of the highest order".
Grainy black and white video shows the wounded the pilot parachuting into Truc Bach Lake where was captured and beaten by the North Vietnamese who brought him ashore. The world will miss John McCain. Few have served their country so well or so long.
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It is an honor to have been able to call Senator McCain my colleague and I am even more proud to have been able to call John my friend.
Obama also recognized McCain's heroism, urging Americans to follow his example. He was a leader to senators from both parties, a touchstone on foreign and domestic issues.
McCain is survived by his wife, Cindy, and seven children; three from his first marriage and four from his marriage to Cindy. Connie and I are thinking of them now.
The patent contempt the two men displayed for each other showed no sign of fading, even as McCain continued to weaken. Senator McCain was a maverick who fought for what he believed in and represented the very best ideals of the United States Senate. McCain corrected her and said Obama was a "decent, family man". "Today, with the passing of John McCain, Congress and America have lost a leader and public servant of deep patriotism, outstanding bravery and undaunted spirit".
Some of the deeply conservative Republicans in the state - the same ones who forced the state GOP to censure McCain earlier in his career for daring to work on bipartisan immigration proposals - are reluctant to entertain suggestions that Cindy McCain take the seat.
McCain was prominent in tech-related issues, joining a group of senator trying to beef up laws around political ads that appear online, after Russian interference in the 2016 election.
On Friday, Republican Mitt Romney said he was "blessed and humbled" to have been friends with McCain.
McCain was elected to the U.S. Senate from Arizona six times.
A police escort accompanied the hearse that carried his body, as a fiery sunset cast its last light over the rustic countryside McCain loved dearly, and local residents came bearing flowers for the late political titan.