However, today marks the first time the Arizona senator has officially declared his intention to run for the Republican party's nomination.
"Today, I announce my candidacy for President of the United States," McCain said at his announcement event in Prescott Park, New Hampshire.
"I do so grateful for the privileges this country has already given me; mindful that I must seek this responsibility for reasons greater than my self-interest; and determined to use every lesson I've learned through hard experience and the history I've witnessed, every inspiration I've drawn from the patriots I've known and the faith that guides me to meet the challenges of our time, and strengthen this great and good nation upon whom all mankind depends."
McCain said he will offer "common sense, conservative and comprehensive solutions" to the "formidable challenges" that face the US.
"I'm prepared for them," the ex-Navy pilot and former Vietnam captive continued. "I'm not the youngest candidate but I am the most experienced.
"I know how the military works, what it can do, what it can do better, and what it should not do. I know how Congress works, and how to make it work for the country and not just the re-election of its members. I know how the world works. I know the good and the evil in it.
"I know how to fight and how to make peace. I know who I am and what I want to do."
McCain said he would also run with a view to reducing the United States' dependence on foreign sources of energy, which he said is "harming our environment and economy [and] endangering our security".
He is also a vocal opponent of the war in Iraq and ran against George W Bush in 1999 for the Republican candidacy in the ill-fated election of 2000 when Bush won after a wrangle between himself and Democrat candidate Al Gore that went up to the Supreme Court.
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