As I pinged around Iowa and heard speeches by all four leading candidates (Sanders, Biden, Elizabeth Warren and Pete Buttigieg), I realized that there are three R’s of this Democratic primary.

There’s revolution, which is what Sanders expressly urges — “revolution” is his mantra — and which Warren less bluntly promotes, calling for “big structural change” and vowing to “take our government back.”

There’s rejuvenation: Buttigieg, 38, leans on the fact that his three main rivals are all 70 or older to stress the importance of a fresh set of eyes and the need to give a new generation of politicians a chance.

And there’s restoration. That’s Biden, the country’s vice president from January 2009 to January 2017. He weaves many references to President Barack Obama into his remarks, mentioning “our administration,” and in a 60-second video that he shows at the start of his events, Obama’s face appears before his does and pops up another two times.

What Biden is promising, though, isn’t so much a return of personnel or policies as of propriety. He wants to make America normal again. He told the Waukee crowd that in Trump’s world, “Up is down, lies are the truth, allies are enemies. Everything is through the looking glass.” He’s going to rescue us from that wicked wonderland. And he’s going to do it by being a really nice guy.

Let Sanders go point by point through the virtues of Medicare for all. Let Warren illuminate the intricacies of her anti-corruption plan. Biden is fuzzier and gooier than that — by design. You’re supposed to leave a Sanders or Warren rally suffused with righteous anger. You leave a Biden rally sort of misty and choked up.

His event in Waukee was arguably most memorable for remarks by Tom Vilsack, the former governor of Iowa, and his wife, Christie, about how loving and supportive Biden had been to their family three years ago, when their 6-year-old granddaughter died. Biden, they said, knows about loss, having buried two of his own children, along with his first wife. It has humbled him. Seasoned him. He senses sorrow and does what he can to soothe it.