In his first campaign for Newark mayor nearly two decades ago, upstart Cory Booker was derided as an over-credentialed outsider who was using the broken city as a steppingstone to higher office.

Yet that is far from the reception Booker received Wednesday at a lengthy and self-congratulatory swearing-in ceremony for Essex County officeholders, including Joseph N. DiVincenzo Jr., the longtime county executive whose political reach extends far beyond the Democratic stronghold.

"And this young man here, there is no question, no question: He's going to be the next president of the United States of America,'' DiVincenzo said at the Donald M. Payne, Sr. School of Technology in Newark. "Listen to me. I know politics. I know Cory Booker. I know when he gets on the debate stage, I know what he's going to do."

As Booker descended from the school stage and into a sea of selfies, he deflected questions about his looming presidential bid.

"Right now, my focus is getting back to D.C. today,'' he said when pressed by a television reporter about his 2020 plans. Right now, a government shutdown was soaking up his energy and attention, and giving him a ready excuse to avoid talking about his own plans.

Booker spent the holiday week officially in mulling-of-options mode, but Massachusetts Sen. Elizabeth Warren's New Year's Eve announcement that she took the first formal step of entering the contest has intensified the spotlight. Suddenly, the lane of populist-sounding progressives just got more crowded.

Booker has been stepping up his pre-campaign profile for almost a year, from crisscrossing the country campaigning for Democratic candidates to his "Spartacus" moment during Supreme Court nominee Brett Kavanaugh's explosive confirmation hearing, a comment that instantly metamorphosed into an Internet meme.

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And Wednesday's appearance in Newark was also another small step of pre-campaign preparations. The onetime outsider, accused of being a Trojan horse for monied interests, was back in the bosom of his political base, showering the local Democratic chieftains with fulsome praise.

On the surface, it seemed like routine politicking, but it had the look and feel of Booker conducting some last-minute due diligence, making sure that he left behind no unhappy locals who will likely be approached in the coming months by national reporters combing through the senator's past.

Booker praised Essex County Democratic Chairman LeRoy Jones' work ethic. He praised Essex County Sheriff Armando Fontoura as a political warrior and called him the "most popular" politician in the county. There were others.

"I can't be more proud of this young guy, what he's done and what he's done in such a short period of time,'' DiVincenzo gushed back.

But the heat of a crowded campaign battlefield awaits. Booker will eventually have his big announcement, followed by the pageantry of a campaign kickoff event. And then comes the scrutiny of his career in Newark, his attempts to turn Newark into a magnet for corporate and philanthropic funds, and his past reliance on Wall Street and Silicon Valley money to finance his campaigns.

That last issue may prove to be a thorny one for Booker as the party's grass-roots activists demand a more confrontational approach to Corporate America. As a campaign surrogate for President Barack Obama in 2012, Booker stunned the political establishment when he defended Bain Capital, the investment firm co-founded by Mitt Romney, Obama's Republican challenger.

Booker has sought to purge that past image by announcing in February that he would no longer accept donations from corporate PACs. Yet, historically, corporate PAC money has represented only a small portion of his fundraising haul, according to OpenSecrets.org, which tracks fundraising for federal candidates.

Between 2013 and 2018, Booker received $2.8 million from the securities industry, but only $62,000 of it came from corporate PAC donors, OpenSecrets reported. Lawyers and law firms contributed $3 million to Booker over the same time period, with $191,000 coming from industry-related PACs.

Warren went further this week, saying Democrats should disavow any funding from "billionaires" in any form, whether from their own donations or from their "super PACs" that they may operate independently from the candidate's campaign.

Asked about Warren's remarks, Booker said, "What I believe is that we need to start shifting American politics to being 1,000 percent focused on people, and what we have right now in this country is horrific campaign finance legislation,'' he said.

He added, "We've got to make sure our elections are about the people, and the best way to do that is broad-scale finance reform."

That's striking a populist chord that should play well with grass-roots activists. But Booker didn't exactly say he closed the door on billionaires. That could change. After all, he's not an official candidate yet.