Former Maryland Gov. Martin O'Malley unveiled an ambitious plan to expand Social Security Friday, pushing others in the Democratic field to stake out policy positions on issues important to older Americans.

The Democratic presidential candidate released a white paper early Friday that detailed a goal to increase the number of Americans with adequate retirement savings by 50 percent within two terms in the Oval Office.

"We cannot ask seniors with modest savings to live on even less," the white paper says. "Instead, we should expand Social Security so they can retire with the dignity they have earned over the course of their working lives."

In order to pay for it, O'Malley proposes to lift the payroll tax cap for people who earn more than $250,000 yearly. The policy outline also repeated his commitment to raising the minimum wage to $15 an hour, which he argues will allow more dollars overall to be contributed.

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The Democratic hopeful's plan is in keeping with Massachusetts Sen. Elizabeth Warren's initial push to expand the Social Security program, and follows in the footsteps of former Iowa Sen. Tom Harkin's proposals to do the same. But with a likely Republican-controlled Congress after 2016, any reforms for the program face an uphill legislative battle.

O'Malley would tie benefits to the Consumer Price Index for the Elderly, which the campaign sees as a "more accurate reflection" of seniors' cost-of-living. And for Americans who have worked at least 30 years, the Democratic contender would raise the minimum benefits to 125 percent of the poverty line. Overall, O'Malley aides say that Social Security benefits could increase by an average of about $60 per month with his plan.

O'Malley also knocked proposals recently gaining support among the Republican presidential field, like privatizing Social Security or raising the retirement age. He specifically pledged to reject calls for either, and added that lifting the retirement age was just "a back-door way to cut benefits for lower-income workers."

The campaign also laid out ways he would protect seniors from fraud, including raising penalties for financially exploiting older Americans.

By contrast, his Democratic opponents -- except Vermont Sen. Bernie Sanders -- have not committed to expanding the social program.

Democratic frontrunner Hillary Clinton has pledged to protect and enhance Social Security, saying at a New Hampshire event in April that "we don't mess with it, and we do not pretend that it is a luxury." But unlike Sanders and O'Malley, Clinton has not specifically endorsed its expansion.

Sanders, meanwhile, has championed the increase of benefits doled out by Social Security, and has proposed raising taxes on the wealthy to fund his plans.

O'Malley has already started drawing praise from liberals for his position.

"'Expand Social Security' should be the mantra of all Democrats in 2016. It's great that Martin O'Malley and Bernie Sanders are both campaigning on this message," Stephanie Taylor, co-founder of the Progressive Change Campaign Committee (PCCC), said in a statement Friday.

O'Malley currently lags behind several Democratic candidates -- and one non-candidate -- in the latest CBS News poll. Among Democratic primary voters, the former Maryland governor is tied with former Rhode Island Gov. Lincoln Chafee at one percent. He trails Clinton, Sanders, Jim Webb, and even Vice President Joe Biden, who is not running for president.