Marlon Marshall, right, one of the White House staffers in charge of enrollment outreach, chairs a meeting on Feb. 7. (Bill O'Leary/The Washington Post)

Two years ago, Marlon Marshall was deputy national field director for President Obama’s disciplined, centralized reelection campaign. His job was to mobilize enthusiastic supporters to do something that cost them nothing: cast a vote.

Now he is at the White House working on a very different, and arguably more difficult, effort: helping persuade Americans to get — and in many cases pay for — health insurance.

Marshall, 34, is deputy director of the White House Office of Public Engagement, where he is charged with helping to sell the Affordable Care Act, which remains politically polarizing and was damaged by a disastrous Web site rollout last fall.

During the presidential campaign, Marshall was known as a consummate organizer who would yell into a bullhorn to motivate his troops. He also would gently chastise them if they underperformed — a move that came to be known as “the swipe.”

But the health-insurance effort is less straightforward, requiring Marshall to coax and prod a broad coalition of advocacy groups and other independent players to help get people enrolled.

“It’s totally different from what we did on the campaign,” said Adam Hoyer, a Florida field director during the campaign who now serves as executive director of Protect Your Care, a group that supports the health-care law.

Marshall’s effort is focused heavily on two dozen cities where the numbers of uninsured Americans are highest. His boss, Paulette Aniskoff, said Marshall uses his “field brain” to “find people who don’t talk to government every day” and find ways to persuade them to obtain coverage.

“At the end of the day, this is a local, city-by-city strategy,” Marshall said in a recent interview, just after wrapping up a staff meeting in the Old Executive Office Building. “It’s not us going out and saying, ‘Do this and do that.’ ”

Having spent nearly his entire career in politics — he even met his fiancée, Stacy Berger, on John F. Kerry’s 2004 presidential campaign — Marshall does not dwell much on the fact that unlike other drives, this is a venture with no clear end in sight, where you are asking people to make “an intensely personal decision that will have an immediate and direct impact on their day-to-day lives.” Not dwelling on the daunting nature of the task might be an asset.

Marshall helms a daily 8:45 a.m. phone call with officials from the White House and the Department of Health and Human Services to track what they are saying about the law and what others are doing to promote it. Later in the day, he and his aides meet in a conference room to run through how they are getting star power — including celebrities, faith leaders and DJs — to spur enrollment.

At 3 p.m. on most Tuesdays, Marshall also joins a meeting of groups working on enrollment. The group meets outside the White House, and Marshall cannot dole out marching orders. But he can suggest where the law’s supporters can boost their efforts — such as the Texas cities of San Antonio, El Paso and McAllen, for example, or in Atlanta.

The world Marshall aims to coordinate — but does not preside over — includes groups such as the Service Employees International Union, Enroll America, the League of United Latin American Citizens and the Planned Parenthood Federation of America. They are looking to find the uninsured, but as Deirdre Schifeling, Planned Parenthood’s national organizing and electoral campaigns director, put it, “There’s no perfect list.”

Enroll America has developed a model — with the aid of some of the technology experts from the president’s 2012 campaign — that aims to identify uninsured residents in a given neighborhood. Chris Wyatt, the group’s managing director, said it means advocates now have about a 30 percent chance of finding a person without coverage when someone opens the door. “That’s half of all the doors we need to knock on,” he said.

About 400 Planned Parenthood canvassers are using that model to knock on 15,000 doors a day in 18 cities; Schifeling said it works 10 to 30 percent of the time. The canvassers come armed with tablets so they can sign people up for an e-mail account and fill out an application for coverage at the end of their initial conversation. Schifeling said canvassers have a 55 percent success rate for enrollments.

It’s a far less precise targeting campaign from the one Marshall helped oversee in past election cycles.

In Washington, Marshall — neatly dressed in a gray pinstriped suit and red tie — was discussing strategic deployments in a recent meeting with his staff. A 6-foot-1 former weight lifter who is now a CrossFit enthusiast, Marshall took sips of water from a reusable bottle crammed with orange and lemon slices as his aides reported their list of activities.

One outlined how an official would buttonhole celebrities at this month’s French state dinner to determine whether they would tout; another described efforts to encourage tweets from Olympic and professional athletes; and a third detailed how Jewish groups would launch events on Feb. 18 because the number 18 symbolizes life in Judaism.

This is the sort of leverage the White House can exercise most easily: three days after the state dinner, actresses Mindy Kaling and Julia Louis-Dreyfus, both of whom attended the event, sent identical Instagram messages showing themselves holding brightly colored heart signs with the words, “My loved ones are covered, are yours?” and “#GetCovered at”

As an undergraduate at the University of Kansas, Marshall first focused on engineering. But in 1998, a senior named Kevin Yoder sought him out in the residence halls to run as a student senator on his slate.

“He was a natural,” said Yoder, now a House Republican in his second term.

A few years later, Marshall led a successful movement to save a 1960s-era student bowling alley from being converted into a cyber café; Yoder cast the deciding vote as chairman of the Student Union Board of Directors. “He was very persuasive,” Yoder said.

Marshall said the experience taught him that “if you want to make change, you organize people.” He went on to push for a committee to examine how to increase diversity in the KU student body. During the 2012 campaign, when things were going well, Marshall would wrap a Jayhawks blanket around his neck and march through his office as the school’s fight song played on his laptop.

While Marshall has put down roots in the District — he bought a house in March in the city’s Eckington neighborhood and is working on it in his spare time — there is no way to overstate his devotion to his home town’s baseball team, the St. Louis Cardinals, and his alma mater. His preferred outfit at home is a Jayhawks hoodie and sweatpants; when asked to sing the KU fight song during an interview, he asks whether a reporter wants the undergrad or alumni version. (He belted out the alma mater version, with verve.)

Seemingly every Democratic operative who has worked with Marshall has a “squeezing blood from a stone” story. At least that’s how Robby Mook, who served as Hillary Rodham Clinton’s director in three crucial swing states, remembers their efforts in Nevada on her behalf in 2008. The team doubled their vote goals to win the caucuses, and Marshall stayed with Clinton until she conceded before joining Obama’s general-election campaign.

Brynne Craig, who worked with Marshall in Nevada and at the Democratic Congressional Campaign Committee, remembers how in 2009 he amassed a huge number of volunteers to pull out a win in what she calls the “most crazy special election ever” in New York’s 23rd Congressional District.

The question now is whether he can accomplish a similar feat for the Affordable Care Act.

“I don’t know that anybody can resuscitate this law from where it is, but I think Marlon is as capable as anybody,” said Yoder, who said he remains “proud” of his former protégé even though he opposes the health-care law. “He’s got his work cut out for him.”