A generation ago, Republicans focused on reforming the nation's safety net by requiring poor mothers to work.

These days, the Trump administration and Republican leaders are once again looking to overhaul government assistance programs. But now they are zeroing in on a new group: low-income men.

Much of the focus this time centers on requiring able-bodied, working age recipients to get jobs or participate in other community activities if they want to receive Medicaid or food stamps -- two of the largest public aid programs in the US with tens of millions of enrollees each.

While women are certainly affected, many mothers can receive exemptions from the new mandates. So the requirements are falling more heavily on men.

"The poster-child mental image [policymakers] are painting is of men, especially young men," said Elizabeth Lower-Basch, director of the income and work supports team at the left-leaning Center for Law and Social Policy.

Conservatives think working-age men who aren't disabled and don't have children should be expected to have jobs.

"In their situation, the failure to work is less justified," said Robert Doar, a poverty studies fellow at the right-leaning American Enterprise Institute, noting the benefits of employment. "Their incomes will go up and they'll be less likely to be poor."

This is just one of the reasons why men are now in Republicans' sights.

Another is the changing nature of the nation's safety net. Historically, welfare programs have been geared toward helping poor families with children, often headed by single mothers. But in recent years, the programs have ballooned in size, with many more men signing up.

Take Medicaid. Prior to Obamacare, it was difficult for adults -- particularly childless adults -- to qualify for the public health insurance program in many states.

But the health reform law's Medicaid expansion opened up the program to low-income Americans in the 31 states that opted to participate. More than three million men gained Medicaid coverage between 2013 and 2016, according to Census Bureau data. And, the uninsured rate for poor, childless men fell to 21.8% in 2015, down from 48.1% in 2013 in states that expanded, according to the Urban Institute.

Related: Thousands of Arkansas Medicaid recipients must start working in June

The Trump administration, however, quickly signaled that it was open to allowing states to impose work requirements on certain beneficiaries for the first time in Medicaid's history. It has approved three state applications so far this year and is reviewing at least eight others.

But not everyone is subject to the new rules. In Kentucky, for instance, pregnant women and primary caregivers of children are excluded. Plus, taking care of an aging parent counts toward the community service requirement. Arkansas, meanwhile, is exempting those who live with dependent children or care for someone who is incapacitated -- roles that often fall to women.

The Trump administration and Republican leaders are positioning work requirements as an opportunity to improve Medicaid recipients' health and financial independence, but consumer advocates say such measures will leave many more Americans uninsured. They also note that many enrollees already work, including 65% of the men in the program, according to the Kaiser Family Foundation. But they earn so little, they still qualify for government help.

The food stamp program has also seen a surge in participation in recent years, particularly among men.

Total enrollment in the Supplemental Nutrition Assistance Program soared following the Great Recession, though it has drifted downward since its fiscal 2013 peak. The number of non-elderly men receiving SNAP benefits stood at 7.2 million in fiscal 2016, up 84% from fiscal 2008, according to federal data. This is in part because former President Barack Obama relaxed the work requirements for enrollees without dependent children.

Now, the Trump administration wants to mandate that more food stamp recipients work. The Agriculture Department is currently seeking comments on how to get more able-bodied, working age adults without dependent children -- 54% of whom are men -- into the labor force. It is weighing limiting the states' ability to waive the work requirement in areas with high unemployment.

Related: Trump administration seeks to require more people to work for food stamps

The agency's "goal is to move individuals and families from SNAP back to the workforce as the best long-term solution to poverty," said Agriculture Secretary Sonny Perdue. "Everyone who receives SNAP deserves an opportunity to become self-sufficient and build a productive, independent life."

However, fewer men are working these days, which is another reason why Republicans are focusing on them. Just under 70% of men are in the labor force -- either in a job or looking for one -- compared to nearly 87% in 1948, when the federal government began measuring the statistic.

The decline is particularly evident among lower-income men, who typically have less education, according to the Brookings Institution. This is in part because many positions today require more than just high school diplomas and skills that most of these men don't have.

Related: Fewer low-income men are working

Blocked from taking up broader entitlement reform by a reluctant Senate, House Speaker Paul Ryan is now recasting the effort as a way to ease the nation's worker shortage. He points to companies and studies that say it's hard to fill vacancies. In an online post last month, Ryan highlighted that seven million men are missing from the workforce, citing an American Enterprise Institute study.

"With so much untapped potential sitting on the sidelines, Congress should continue to advance policies that incentivize work, foster independence, and help people escape poverty," he said.

Adding more men to the labor force would also chip away at several societal problems, said Lawrence Mead, a professor of politics and public policy. Fewer would be poor, doing drugs or committing crimes, while more would be with their families or paying child support.

"All of this can only be addressed if we get these guys working," Mead said.

Correction: An earlier version of this article included the total number of males who received benefits from the Supplemental Nutrition Assistance Program, including children. That number has been changed to include only men between the ages of 18 and 59 who received food stamps.