President Clinton, in his primetime speech at the Democratic National Convention, called on Americans to bring in a “breath of fresh air” in the form of the Harris-Walz ticket. Mr. Clinton, who has grown quieter and more hoarse in his older years, warned Democrats not to be complacent like they were eight years ago. 

“I don’t know how many of these I have left,” the former president said with a smile, noting that he had been to every convention since 1972. He said he wanted to see nothing more than that new generation of leadership. 

“If you can bring in this fresh air, you won’t regret it for the rest of your life, your children won’t regret it, your grandchildren won’t regret it,” Mr. Clinton said to raucous applause. “We’re gonna walk out of here feeling pretty good,” he added. “We have to find a way to go forward together, where we the people make our union more perfect.”

Mr. Clinton’s most famous address to a national convention — beyond his own — was his 2012 address to make the case for President Obama. After that 45-minute address, Democrats left the hall feeling energized and ready to win. That speech led Mr. Obama to dub Mr. Clinton the “Explainer-in-Chief.”

Mr. Clinton used that moniker to mock President Trump, who Mr. Clinton says would do nothing more than spend another four years forcing his personal grievances into Americans’ everyday lives. Ms. Harris is “for the people” and Trump is for “me, myself, and I,” Mr. Clinton said. 

“Donald Trump has been a paragon of consistency … he creates chaos and then he kinds of curates it as if it were precious art,” the 42nd president warned, adding that Ms. Harris has the “vision, experience, the temperament, the will, and yes, the sheer joy.”

“He mostly talks about himself. Next time you hear it, don’t count the lies — count the ‘I’s,’” Mr. Clinton said. “When Kamala Harris is president, every day will begin with: ‘you, you, you, you.’”

“Do you want to spend the next four years talking about crowd size?” he joked. 

On his title as “Explainer-in-Chief,” the former president said that even he couldn’t explain some of Trump’s more eccentric moments. “What are [foreign leaders] to make of these references to the ‘late, great Hannibal Lecter’?” Mr. Clinton said, referring to Trump’s unexplained rally references to Anthony Hopkins’ Oscar-winning performance. “President Obama gave me the great honor of naming me the ‘Explainer in Chief,’ but for the life of me even I can’t figure out what that means.”

Mr. Clinton also took the chance to praise the choice of Governor Walz as the vice presidential nominee, saying Ms. Harris had “knocked it out of the park” with what he called her “first presidential decision.”