MASON CITY, Iowa — Senator Cory Booker glided into the state first, offering himself as a herald of peace in a northern Iowa church that advertised “radical hospitality” on its marquee. As a rainbow cracked the frozen sky outside, Mr. Booker spoke of restoring “grace and decency” and erasing “the lines that people think divide us — racial lines, religious lines, geographic lines.”

Senator Elizabeth Warren arrived soon after, still thrumming with the energy of a weekend announcement speech in Lawrence, Mass. Having vowed there to “fight my heart out” against government corruption and corporate power, Ms. Warren roused the crowd in Cedar Rapids on Sunday not with bounteous optimism but a call to arms.

“This is the time,” she said, “to take on the fight.”

In the space of a weekend, the two Democrats mapped the philosophical and temperamental fork their party must navigate as it challenges President Trump. Down one path, Mr. Booker’s, lies a mission of healing and hope, with a campaign to bind up social wounds that have deepened in the Trump era. The other path, Ms. Warren’s, promises combat and more combat — a crusade not just to defeat Mr. Trump but to demolish the architecture of his government.

As much as any disputation over policy, this gulf defines the Democratic field, separating candidates of disparate backgrounds and ideologies into two loose groups: fighters and healers.

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It is perhaps not an accident that the most confident Democratic tribunes of good feeling are all men, while the party’s sternest warriors are mainly women. In a contest for the presidency, a position traditionally viewed in martial terms, it may be easier for a man of Mr. Biden’s backslapping swagger or Mr. Booker’s athletic stature to show tenderness or vulnerability without fear of appearing weak.

And it was with enthusiastic physicality, and regular references to having played high school and college football, that Mr. Booker preached love and understanding. He clasped his chest and his face at moments of emotion, usually stirring murmurs of appreciation and sympathy; in one case, he wrapped his arm around a voter for a midspeech selfie. While Mr. Booker said he was ready to spar with Mr. Trump, stating matter-of-factly that “there is nobody in this race tougher than me,” his overarching theme was about reconciliation.

At an airy adult learning center in Waterloo, Mr. Booker insisted that the capacity to conquer all manner of hardships was within human reach — a contrast with Ms. Warren and other populists, who tend to describe ordinary people being stripped of power by big institutions.

“The most common way people give up their power,” Mr. Booker said, “is not realizing that they have it.”

Forces of darkness appeared in Mr. Booker’s political narrative — the country, he said, has a “cancer on our soul” — but there were few villains. Where malignant people intruded, Mr. Booker leavened their presence with humor: Strom Thurmond, the South Carolina senator who embodied virulent racism, became the subject of a laughter-inducing vocal impression. Describing how a racist white real estate agent directed a dog to attack his father, Mr. Booker added a punch line: Each time his father told the story, he joked, “that dog got bigger!”

“She is a fighter, but I think that will also unite the country, if we’re fighting for the right purpose,” Ms. Garlock said. “Her purpose is to help regular people who are going to work every day, trying to pay their bills, which is the majority of this country.”

Both approaches have a rich history in Democratic politics, nationally and in Iowa — a state that has helped elevate conciliators like Jimmy Carter and Barack Obama to the presidency, while for decades sending prairie populists like Tom Harkin to Congress.

Mr. Booker shares a clear political lineage with Mr. Obama, who captured the Iowa caucuses in 2008 with a message of national unity. But the party has also shifted left since then, and has grown more suspicious of Republicans who harried Mr. Obama and elected Mr. Trump. In 2016, Mr. Sanders nearly upset Hillary Clinton in Iowa as a populist insurgent.

Mr. Trump’s slashing style may also weigh on primary voters and caucusgoers, Democrats say, guaranteeing that even a kindhearted nominee would face a blizzard of personal attacks and crude trash-talking.

Still, Representative Dave Loebsack, a veteran Democrat whose district covers Iowa’s southeastern quadrant, said he believed that even partisan Iowans yearned for political reconciliation. Though he is neutral in the race, Mr. Loebsack predicted that Mr. Booker’s uplifting narrative would resonate.

“I think we have to be careful with anger and outrage and alienation because that can also feed into the worst instincts of folks,” Mr. Loebsack said, adding of Mr. Booker: “I love his message of love and redemption and all the rest.”