WASHINGTON — Cory Booker arrived in Washington pledging to heal festering political divides, writing a book called United, and lighting up social media with pictures of his dinner with the hard-right Texas Sen. Ted Cruz.
But nearly four years later, as he stakes his claim as a young Democratic leader and builds toward a potential run for president in 2020, the New Jersey senator's signature brand of uplift and positivity is running into a party base eager for combat.
The contrast between Booker and some fellow Democrats was illustrated Tuesday, when he joined a raft of party heavyweights who spoke to a Center for American Progress conference packed with feisty liberals.
Elizabeth Warren, the pugilistic Massachusetts senator, decried the money that "slithers through Washington like a snake" and lobbyists who "swarm" like "a plague of locusts" and went right after President Trump, declaring, "Our government is not a plaything to make him richer."
Rep. Maxine Waters (D., Calif.) won a standing ovation later with a call to impeach the president.
Booker, up next, insisted that Democrats could not be defined only by battling Trump.
"There are real issues that necessitate us resisting and us fighting, but I want to let you all know that our party cannot just be about that," he told the crowd. "Trump is a symptom of a problem, he's not the problem."
But the confrontational atmosphere in Washington, at town halls, and at protests ringing out across the country raises questions about whether that tone, which has carried Booker so far, will work in this moment as he tries to push onto the national stage.
"His natural inclination is one of inspiration," said John Podesta, who chaired Hillary Clinton's 2016 campaign and said he is a "big fan" of Booker's. "But you've also got to inspire people to oppose things that are really terrible for the country."
Republican pollster Frank Luntz said the country as a whole might welcome a call to unity, but doubted it would satisfy a roiling liberal base.
"Booker is not a yeller," he said. "Booker is a consensus driver, which makes him perfect for a general election but makes winning a primary very difficult."
That Booker had a keynote slot at an event drawing the eyes of Democratic elders and activists speaks to his potential power within a party that, for the first time in years, is without an obvious leader. As a bevy of ambitious senators, mayors, and governors vie to fill that void, Booker, 48, is one of the most prominent faces of a younger generation of potential national candidates.
Many, including California Sen. Kamala Harris, Minnesota Sen. Amy Klobuchar, and Los Angeles Mayor Eric Garcetti, also spoke at the Washington confab.
Booker's bet on lofty rhetoric — calling, for example, for Democrats to be the party "that reignites that conviction that this will be the country of impossible dreams" — could be "refreshing" for voters seeking a contrast to the vituperative Trump, said Brigid Harrison, a political science professor at Montclair State University.
And Luntz said the senator's natural political talent gives him immense potential.
"If America votes for the best speaker in 2020, they would vote for Cory Booker," Luntz said. "He really is that good."
And he has done his share of battling Trump this year. Most notably, he testified against fellow Sen. Jeff Sessions when the Alabaman was tapped to become attorney general — a move some saw as an early marker in the presidential jockeying — and voted against nearly every one of the president's cabinet picks. He has forcefully denounced Trump's firing of FBI Director James Comey.
But conflict doesn't come naturally to Booker, who responds to Twitter insults by telling critics he loves them.
Any sign of softness on Trump's part could add to the skepticism of some factions on the left that chafe at Booker's ties to Wall Street and Silicon Valley elites, and who might note that Ivanka Trump and Jared Kushner backed his 2013 Senate run.
Booker also brought on a liberal storm earlier this year when he voted against a Bernie Sanders proposal to ease the import of prescription drugs from Canada. The swift reaction showed the political risk of angering the liberal base, and Booker quickly tried to make up for it by joining the Vermont senator to introduce a new bill on the issue.
Robert Shrum, who advised both Al Gore and John Kerry in their presidential campaigns, said the next Democratic nominee will have to go beyond fighting, and try to address the economic worries Trump tapped into.
"It's not just about opposing Trump, it's about articulating a message on economic and social justice that reaches people," said Shrum, formerly of New Jersey.
Sanders and Warren have long paired their attacks on banks and elites with calls to fight for the common person.
Booker tested similar themes Tuesday, telling the audience at a Four Seasons ballroom, "We've got to be focused on those folks in inner cities, in factory towns, the grassroots of our country. That's where our attention needs to be."
Booker allies insist that he is not building his plans around a run for president. Rather than focus on key primary states, they note, his travels this year have brought him to places such as Hawaii, Montana, and New Mexico, as well as Florida, where he has stumped for fellow Democrats trying to hold their Senate seats. (Booker did make time, however, for a California fund-raiser recently while accepting an award from the Humane Society.)
"His focus is primarily on protecting his colleagues," said longtime Booker political aide Modia Butler.
He got the question again Monday after delivering the University of Pennsylvania's commencement address. The speech had all of Booker's hallmarks: quotes from Gandhi and King, jokes about his veganism, and a Lord of the Rings reference. He came close to mentioning Trump only once.
"Can you be a person whose love is so great, that you love those people you disagree with?" Booker asked the new graduates. "Can you sit down with someone who's wearing a red Make America Great Again hat and make a conversation?"