U.S. Sen. Cory Booker, D-N.J., says he got his Ph.D. on the streets of Newark.

Now he's about to roam the prairie in Iowa this weekend, testing out for the first time the core themes of his 2020 campaign for president.

Booker will begin a two-day "Iowa Rise" tour Friday in places including Waterloo, Mason City and Marshalltown, planning to extol his "lead with love" gospel among a restive, combative Democratic base that wants to confront President Donald Trump, not cooperate with him. Iowa caucuses a year from now will kick off the 2020 presidential campaign.

"Right now, people fear that the lines that divide us are growing stronger than the ties that bind us,'' reads a news release announcing Booker's "Iowa Rise" tour. "He believes that the answer to our common pain is to reignite our sense of common purpose to build a more fair and just nation for everyone."

It's not the first time that this appeal to higher civic purpose and unity was made to Iowa Democrats by a prominent African-American political celebrity. In 2008, then-U.S. Sen. Barack Obama pulled off a surprise victory in the Iowa caucuses with a similar and inspirational "hope and change" message.

"There’s always somebody to tell why the system can’t change,” Obama said in Iowa 12 years ago. “If you are not willing to accept what the cynics say, we will heal this nation. We will repair the world.”

That victory certified Obama as a bona-fide contender, and he would go on to defeat rivals John Edwards and Hillary Clinton in hard-fought primaries that spring.

But this time around, Booker, the charismatic former Newark mayor, will find it harder to replicate the Obama playbook. He is facing a far more crowded field of contenders, some of whom are political celebrities in their own right and honing their own progressive-theme messages of change.

In 2008, a surge of young, first-time "Generation X" voters swamped polling places, most of them drawn to Obama's message. In 2020, a combination of millennial voters and moderates disgusted with Trump's nationalism and demagogy are expected to lead the surge, and they'll have plenty of candidates to choose from.

"Booker comes across as a dynamic candidate, the kind of candidate many Iowa Democrats find appealing," said David Redlawsk, a University of Delaware political scientist and author of book on the history of the Iowa caucuses. But, he added, "he is not the only one in that lane."

Booker is no stranger to Iowa. He swept through the state last October as part of a nationwide fundraising tour for congressional candidates. He also toured the state in 2016 as a surrogate for Hillary Clinton, and last October was the keynote speaker for the Iowa Democratic Party's fall gala, where he brought 1,100 party members to their feet with his rousing "Be faithful" mantra.

That visit came amid Booker's star turn as a Senate Judiciary Committee member who grilled Supreme Court nominee Brett Kavanaugh, who was accused of sexual misconduct as a teenager at a Washington, D.C. area prep school. Booker seized the spotlight by releasing confidential documents in defiance of Senate rules and comparing himself to Spartacus, the leader of a Roman slave revolt.

That comment turned Booker into a target of derision on the internet yet also planted him front and center in the cable news cycles. He was also not the lone 2020 hopeful on the Senate panel.

The hearing also elevated the profiles of Sens. Kamala Harris, D-Calif., who jumped into the race last month, and Amy Klobuchar, D-Minn., who is expected to announce her candidacy Saturday.

And there is little evidence, so far, that Booker's celebrity or his past visits have produced much of a benefit in Iowa. An Emerson College poll of 260 likely Democratic caucus-goers last week said only 4 percent were supporting Booker. That placed him in sixth place and far behind the top choice, former Vice President Joe Biden, with 29 percent support.

Booker didn't fare much better in a Des Moines Register poll in December. That poll also said a majority of caucus-goers preferred a candidate deemed to have the best chance of winning the general election over a candidate who shared their values. That's nearly a reversal from four years ago, the poll said.

"My reaction to that is it’s entirely a reaction to Donald Trump in this experiment, with an outsider who’s never been involved in politics or government before and, from a Democrat’s perspective, how disastrous that’s been for the country," Norm Sterzenbach, a former executive director of the Iowa Democratic Party, told the Register. "It seems like Iowa Democrats are not interested in taking a chance again."

Sterzenbach said he had anticipated that newer, fresher names like Harris and Booker would shine early on in the caucus process but then ultimately give way to the more experienced and seasoned candidates closer to caucus day.

"I find it very interesting that people are already sort of there — or at least half of them are already there — in wanting somebody more experienced," he said.

Booker has also pledged to work with Republicans to break the D.C. gridlock, a theme that might seem out of sync with the more combative mood of grass-roots activists. But the Emerson poll also suggested that it might work to his advantage in Iowa; nearly 86 percent of Democratic caucus-goers said they want a candidate who will work across the aisle.

Booker eagerly touts the recent criminal justice reform that Trump signed into law. Booker was an early champion of the overhaul. And for years he has cultivated relationships with Republicans.

“We’ve got to stop the trash talking, the Twitter trolling and tearing folks down,” Booker said in a news conference in Newark last week. “This is the time for all of us to think about our own role in putting the indivisible back in this nation.”

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