Martin O'Malley's policy paper fleshes out his plan to expand Social Security and cajoles front-runner Hillary Clinton to take a similar position.

(Bloomberg Politics) — Martin O’Malley released a policy paper Friday fleshing out his plan to expanding Social Security, elevating the issue in the Democratic presidential contest and motivating progressive activists to call on front-runner Hillary Clinton to take a similar position.

His proposal: raise the base Social Security benefit to 125 percent of the poverty line for Americans who have worked for at least three decades. To finance it, he’d lift the current payroll tax cap on incomes above $250,000.

The position places the former Maryland governor in a similar camp as Vermont Senator Bernie Sanders. Clinton hasn’t taken a position on expansion but recently said in New Hampshire that she’s open to lifting the payroll tax cap, according to the Washington Post. She also told the AFL-CIO that when it comes to Social Security, she’d “enhance it to meet new realities,” without getting more specific, per Reuters.

O’Malley took a veiled shot at Clinton in a Friday op-ed for the Iowa-based Quad City Times, saying he supports “expanding Social Security benefits—not cutting them or merely ‘enhancing them’—to provide a foundation for a more secure retirement to all those who have worked hard to achieve it.” (A Clinton campaign spokesman didn’t immediately return messages seeking comment.)

His plan rejects privatizing Social Security or cuts such as slowing the growth of benefits or raising the retirement age in order to keep the program funded. The program is solvent through 2034, according to its latest trustees report. O’Malley’s plan also seeks to improve worker access to retirement savings accounts.

The move is vintage O’Malley, a policy nerd at heart who has lacked Clinton’s towering presence and Sanders’ pizzazz on the campaign trail. Stuck at 1 or 2 percent in the polls as he barnstorms the country, O’Malley has sought to win the battle of progressive ideas by being the first to release comprehensive and far-reaching white papers on matters like climate change, college affordability and immigration.

O’Malley’s Social Security plan was welcomed by progressive groups.

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The Progressive Change Campaign Committee, said it was “great” that O’Malley and Sanders are pushing the issue and hoped Clinton would join them. Democracy For America said the issue “should be a no-brainer for any 2016 Democratic candidate.” MoveOn.org spokesman Nick Berning said, “Secretary Clinton should join with Elizabeth Warren, Bernie Sanders, Martin O’Malley, Robert Reich, and many other leading voices in calling decisively for the expansion of Social Security.”

O’Malley’s other white papers have enjoyed similar praise from progressives, but so far they haven’t translated to higher polls numbers in a field dominated by Clinton and where Sanders has largely owned the space to her left.

“It’s not the sky that’s falling. It’s the floor that’s falling out from under our seniors,” O’Malley wrote in the Quad City Times. “As Democrats, it is time to stand up for our values and call for the expansionof Social Security for all beneficiaries.”

For Republicans, expanding Social Security is a nonstarter as it involves tax increases. Many GOP presidential candidates have proposed cuts such as raising the retirement age and further means testing. New Jersey Governor Chris Christie, who’s making it a key issue in his campaign, has said those who won’t consider such proposals “don’t care whether Social Security stays solvent and is really there for the people who really need it.”

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