Interviews for this story were originally conducted in 2017.

Democratic presidential candidate Pete Buttigieg told MSNBC's Rachel Maddow Monday night that a national public service program for all young adults could help unify Americans of different backgrounds.

"We really want to talk about the threat to social cohesion that helps characterize this presidency but also just this era," the mayor of South Bend, Indiana, said. "One thing we could do that would change that would be to make it — if not legally obligatory but certainly a social norm — that anybody after they're 18 spends a year in national service."

The 2020 contender is not the first to make this proposal. Service advocates, military veterans and political commentators have argued that a large-scale national service program — which would either encourage or mandate that young Americans spend time in military or civilian service — could help unite the country. The idea gained traction as a solution to decline in civic participation and especially after 9/11. In the fall of 2017, amid the nation's widening political rift, search interest for mandatory national service was at a five-year high, though it has since dipped, according to Google trends.

The Universal National Service Act, which would require people living in the U.S. "between the ages of 18 and 25 to perform a 2-year period of national service, unless exempted, either through military service or through civilian service," was sponsored by Rep. Charles Rangel, D-N.Y., in 2013. It did not make it to a floor vote and Rangel has since retired.

Such a program should, in theory, appeal to both parties — the idealism speaking to Democrats, and the service component drawing in conservatives, said Robert Litan, a non-resident senior fellow at the Brookings Institution, a non-profit think tank. But he's skeptical it would get much traction in the current political climate under President Donald Trump.

Republicans and Democrats are further apart ideologically than at any point in more than two decades, according to a 2017 analysis from the Pew Research Center.

"It needs to be bipartisan. If we had a different Republican president or a Democratic president, I think you would get a more enthusiastic response," he said.

Trump is unlikely to call for such a program, anyway — his 2020 budget proposes to eliminate the Corporation for National and Community Service (CNCS), the agency that runs AmeriCorps.

America’s young population is growing increasingly diverse but also more segregated, a 2016 analysis by the Brookings Institution Metropolitan Policy Program found. Litan said he would settle for a larger scale voluntary national program but believes the "social advantages" of a mandatory one would be "far greater."

Proponents say a voluntary program sizable enough to offer a spot to everyone who desired to participate would provide important societal benefits and could be the social glue the country needs, a rite of passage to bring together people from diverse backgrounds in pursuit of the common good.

"It would create a virtuous cycle," Litan said, adding that people from different socioeconomic, racial and ethnic backgrounds working together to improve society "would help bring us together gradually over time."

However, civilian service could mean diminished earnings for young adults just starting out. And requiring military service could also come with great costs, given that U.S. troops remain deployed all over the globe.

Detractors also argue compelling American youth into service positions restricts individual liberties, pointing to the 13th Amendment, which states:

"Neither slavery nor involuntary servitude, except as a punishment for crime whereof the party shall have been duly convicted, shall exist within the United States, or any place subject to their jurisdiction."

Civilian service

There are already government programs that give people the option to serve outside the military, such as AmeriCorps, the Peace Corps and FEMA Corps.

Benefits include student loan forgiveness — but you must work for 10 years at an eligible nonprofit or government agency while making steady student loan payments (serving as a full-time AmeriCorps or Peace Corps volunteer counts as qualifying employment). While AmeriCorps places more than 80,000 people a year in positions, it receives far more applicants than it accepts.

OPINION:I served my country with AmeriCorps. In return, Uncle Sam sent me a bill.

"I think it's very much an American tradition to want to help," said Shirley Sagawa, president and CEO of the non-profit Service Year Alliance, who also helped lead the development of AmeriCorps. "Unfortunately, there's not enough positions right now."

Sagawa said her organization's goal is to increase access to service opportunities, which she hopes will foster a widespread culture of service.

"We would like every young person to say, 'wow, where am I going to serve?' And be planning to serve," she said. Ideally in the future, "you wouldn't dream of electing a president who hasn't served somewhere."

Military service

Americans who fight to protect the country and its ideals are becoming more rare. The share of the population that has served in the military has fallen by more than half since 1980, according to Pew. Active duty numbers are down from more than 3 million in 1966, when there was a draft for the Vietnam War, to 1.3 million today. President Trump, Barack Obama and Bill Clinton never served.

Compulsory military service has been done before in the USA and is present policy elsewhere in the world.

The U.S. has instituted the draft at various times in its history, but has had an all-volunteer military for decades. The Selective Service System remains in place, however, through which men ages 18 to 25 register. But with the current male-only draft requirement declared unconstitutional, Congress will have to decide whether to eliminate Selective Service registration or expand it to women.

Many developed and developing countries have some form of national service. In Israel, eligible men and women are drafted into the Israel Defense Forces at age 18. Sweden announced in 2017 it was reintroducing compulsory military service, and including women in its conscription for the first time.

If there were a national service program in place in the U.S., Litan said integrating it into the country's homeland security strategy would be important.

The downsides?

Advocates, including Litan, say national service participants should be paid a modest income, and could receive benefits not unlike the GI bill — a law that provides educational and training benefits for military veterans. Though he and Sagawa acknowledge that such a program would require a significant federal contribution, both argue the benefits outweigh the costs.

An analysis commissioned by the National Park Service found if the government were to reduce the backlog of maintenance on public lands using conservation corps (made up of 18- to 25-year-olds considering land management as a career) rather than contractors of National Park Service crews, it would save more than 80% per project.

But economic debates are not the only barriers.

"I'm concerned about the continued erosion of the rights and liberties of 18- to 21-year-olds in this country," said Mack Mariani, political science chair at Xavier University. "We find it much easier to restrict the rights and liberties and impose new responsibilities on the young rather than deal with problems ourselves."

Even Sagawa doesn't advocate for a mandatory program, noting that some young people face obstacles — working to support a single mother, for instance — that would make service nearly impossible.

"People have family responsibilities. ... There are just issues that people have in their lives that people have to be respectful of," she said.

Some also fear such a program might make people think that civilian service should fall only on youth or is a once-in-your-life obligation.

"I think service shouldn't be something that you do and you check the box and you're done with it," Mariani said. "Service is part of an attitude. It's part of a broader culture that people do throughout their lives."

The upsides?

There is healthy debate around the idea of a national service program. What is agreed upon is that service itself is deeply American, and if we did more of it, shoulder to shoulder with people we might never interact with otherwise, we wouldn't just feed hungry mouths and teach eager children — we may heal the nation's unprecedented polarization.

As the late Sen. John McCain, R-Ariz, who has logged both military and public service, said after receiving the Liberty Medal in 2017:

"What a privilege it is to serve this big, boisterous, brawling, intemperate, striving, daring, beautiful, bountiful, brave, magnificent country. With all our flaws, all our mistakes, with all the frailties of human nature as much on display as our virtues, with all the rancor and anger of our politics, we are blessed."

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