Story highlights The former presidents have developed a friendship over the years

Clinton: "We all vote for the gridlock we say we hate"

Washington (CNN) Former Presidents Bill Clinton and George W. Bush spoke together Thursday afternoon at a public event at the Bush Center on the qualities of leadership.

Event moderator, billionaire David Rubenstein, asked the two at the scholastic leadership event in Dallas about what they viewed as the most important quality for someone who wants to be President. Both stressed the virtue of humility.

"I think it's really important to know what you don't know and listen to people who do know what you don't know," Bush said.

Clinton -- who, like Bush, didn't mention President Donald Trump -- agreed that officeholders need to be humble, and warned that those "who are real arrogant in office" have forgotten that history will be their judge.

"If you want to be President, realize it's about the people, not about you," Clinton said. "You want to be able to say, 'People were better off when I quit.' ... You don't want to say 'God, look at all the people I beat.'"

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