WASHINGTON — Sen. Cory Booker is used to making a splash.

But his presidential campaign is off to a subdued start, lacking the viral moments and media attention the New Jersey Democrat typically attracts.

Now, he’s trying something less glamorous. After an initial roll-out centered on his biography and inspirational message of unity, Booker and his aides are stressing the nuts-and-bolts aspects of campaigning and governing. On a conference call Thursday they emphasized staffing levels and early campaign hires, and on Saturday, Booker will launch a “Justice for All” tour to fill out his policy agenda and bring it to critical states, including Iowa, Georgia, and Nevada.

In doing so, the campaign is trying to showcase a different side of a senator whose oratory can stir emotion and charm crowds, but who has faced questions about his abilities as a manager and policy maker — and who, despite a high starting profile, has lagged some rivals in early buzz and fund-raising.

“We need to turn sentiment into substance,” Booker said last week at the Nation Action Network conference staged by activist Al Sharpton.

The policy tour, beginning in his hometown of Newark, comes as Booker’s public polling has remained essentially flat — with around 3 percent to 5 percent support in the crowded Democratic field, leaving him outside the top tier of candidates, while competitors such as Pete Buttigieg, the mayor of South Bend, Ind., and Sen. Kamala Harris of California have surged into the spotlight.

Patrick Murray, director of the Monmouth University Polling Institute, said Booker’s attempt to build his policy profile fits with a Democratic electorate that has told pollsters it is looking first and foremost for someone who can win.

“They want somebody who can inspire them, but they also want someone who can govern and beat Trump and doesn’t look like a flash in the pan," Murray said. “I think this is all part of the long game that the Booker campaign is playing."

Booker’s tour is expected to emphasize and expand upon the issues of racial and social inequality he has long stressed.

His most ambitious plan is a call for “baby bonds," a $60 billion-per-year proposal to give every newborn a government-funded savings account, with more money going to the poorest. The aim is to help close wealth gaps that leave black and Hispanic people drastically behind whites when it comes to home ownership, retirement savings, and student loan debt. The accounts could be used at age 18 for education, homes, retirement, or other investments that build long-term wealth.

Booker would pay for the idea by raising taxes on some of the wealthiest estates and heirs.

Booker has also called for legalizing marijuana and reforming criminal sentencing laws to reduce disparities in punishments for white and minority offenders. He plans to roll out more ideas on voting rights, abortion, and the environment on his tour, highlighting how issues such as climate change disproportionately affect minority and low-income communities in urban and rural areas, according to people familiar with his plans.

Booker’s agenda will face stiff competition for attention in a crowded primary in which the economy, health care, and the environment have consistently rated as Democratic voters’ top concerns.

Sen. Bernie Sanders (Ind., Vt.) on Wednesday launched his latest Medicare for All pitch, an idea that has captivated many liberals. Sen. Elizabeth Warren of Massachusetts has rolled out a slew of plans, including significant tax hikes on the wealthy and largest corporations, breaking up big businesses, and a major program to build affordable housing. Harris wants to boost teacher pay, and Sen. Amy Klobuchar of Minnesota is pitching a $1 trillion infrastructure program.

Booker’s ideas may resonate with black voters who make up a significant portion of the electorate in Nevada and South Carolina, the third and fourth states in the Democratic primary season, as well as in the many Southern states due to vote on Super Tuesday, March 3, 2020, said Brigid Harrison, a political scientist at Montclair State University. Booker has made it clear that South Carolina is critical to his campaign strategy.

Social justice "is a high-salience issue not just for African American voters but also for young people,” Harrison said.

In recent weeks, Booker has dropped in polls as competitors like Buttigieg and Beto O’Rourke have enjoyed publicity boomlets from their announcements.

A Monmouth University Poll released Thursday found that only 3 percent of Iowa Democrats rated Booker as their first choice, eighth best. Just 2 percent saw income inequality as one of their top concerns, while health care (51 percent) and climate change (17 percent) led.

Booker aides on Thursday faced repeated questions from reporters about the senator’s failure to move the needle so far and his $5 million fund-raising haul for the first quarter of the year.

With 298 days to go before Iowa holds the first caucuses, it’s far too early to worry about polls, said Booker’s campaign manager, Adissu Demissie. He said the campaign met its early fund-raising target and has emphasized contact with voters in early states — including calling into Iowa book club meetings — over raising money.

Most of all, he stressed that Booker wants to peak when voting begins in 2020, not now.

“You’ve got to organize and get hot at the end, and that is sort of the philosophy of our campaign,” Demissie told reporters on a conference call.

Booker’s first-quarter fund-raising trailed Sanders’ ($18.2 million) and Harris’ ($12 million), and even that of less high-profile candidates such as Buttigieg ($7 million) and Klobuchar ($5.2 million).

Of course, presidential campaigns are long. Candidates building buzz now risk peaking too soon, said Mo Elleithee, a longtime Democratic political aide who now heads Georgetown University’s Institute of Politics and Public Service.

“He will have his moments to shine or his moments to fall flat on his face," Elleithee said, “but he doesn’t need them now.”