McCain showed "strength of character and perseverance" necessary to lead the nation, Bush said in remarks in the White House Rose Garden. "That's exactly what we need in a president -- somebody who can handle the tough decisions .... and won't flinch in the face of danger."
McCain dined at the White House with Bush a day after sweeping primaries in Ohio, Texas, Rhode Island and Vermont to surpass the 1,191-delegate threshold needed to capture the nomination during the GOP convention in September.
Bush, who blocked McCain from getting the GOP nomination eight years ago, greeted the senator warmly as he reached the portico. McCain said he was "honored and humbled" to receive Bush's endorsement.
He said he intended to have as many joint appearances as possible "as in keeping with the president's heavy schedule."
"Whatever he wants me to do I'll do," Bush said. "I want him to win."
But, he said, "I do have a day job ... and I've got a lot to do."