“What’s called me to run for president is because I think we need a revival of civic grace. We need to reignite a more courageous empathy,” Booker told a recent Democratic gathering at a downtown arcade here, where his presentation was punctuated by eruptions of video games. “We need to understand that old African saying that if you want to go fast, go alone, but if you want to go far, go together.”

On the stump, Booker weaves a spellbinding argument with his call to unity and collective decency. He starts with how his own destiny was changed by a volunteer lawyer who helped his parents buy the home of their dreams at a time when New Jersey real estate agents steered African Americans away from white neighborhoods. He touts his work with unlikely allies, such as conservative Sen. Charles E. Grassley (R-Iowa), with whom he advanced recent criminal-justice reforms.

His appeal to our better selves sets him apart in a combative Democratic field that now features nearly a dozen candidates and is growing by the week. Booker is not answering the populism of the right with an equally fierce version from the left.