Word has it that Democrats are set to take a shellacking in the 2014 elections, in part because midterm electorates tend to be older and whiter. So what if Dems campaigned on expanding Social Security, rather than allowing themselves to get drawn into another debate over how much to cut the program?

There’s a hook for this looming: The coming battle over disability insurance, which is a part of Social Security.

Dem Senator Sherrod Brown, a member of the Finance Committee, tells me that GOP Senators have requested hearings into Social Security Disability Insurance this summer. Dems expect Republicans to attack the program as wasteful and fraudulent, in part because conservative media have already done so, and in part because at least one GOP proposal in recent days took aim at the program.

Brown says Dems should seize this occasion to get behind a proposal that would lift or change the payroll tax cap, meaning higher earners would pay more, while adopting a new measure for inflation that would increase benefits for all seniors. Instead of getting drawn into debates about “Chained CPI” and other entitlement cuts, Brown says, Dems should make the case that stagnating wages and declining pensions and savings demand an expansion of social insurance.

“We should stop playing defense on Social Security, and instead talk about why Social Security is a public pension that we should be proud of, that has lifted tens of millions of people out of poverty,” Brown tells me. “The three-legged stool — Social Security, pensions, private savings — has seen two of the legs sawed off for a large number of people. It’s time to look at expanding Social Security as an issue of retirement security.”

Brown said he expects Republicans to renew attacks on disability insurance (as opposed to the retirement security portion) to divide supporters of Social Security and renew the push for structural changes to the program, and said Dems could use that to draw an effective contrast. SSDI’s trust fund is set to be depleted soon, but that could be solved by a reallocation fix that’s been done before, rather than a deep benefits cut, which Republicans may press for.

“They want to separate ‘good’ Social Security (retirement security) from ‘bad’ Social Security (disability insurance), to win support for structural reform,” said Brown, who is holding a Senate Finance sub-committee hearing tomorrow on the overall program. “The attacks on disability insurance will accelerate. This is how they will try to back-door the dismantling of social insurance. But the public is with us on social insurance.”

Brown noted that such an issue could play well in the midterms. “The electorate is older, so the field is fertile for Democrats to talk about this,” he said. “We should turn up the volume.”

Two Democrats in tough Senate races — Mark Begich and Jeff Merkley – have already staked out aggressive postures on expanding Social Security. It’s also supported by Elizabeth Warren and Tom Harkin, and 70 members of the Congressional Progressive Caucus.

Expanding Social Security would have to be paid for by lifting or changing the cap or some other means, which could leave Dems vulnerable to charges they are raising taxes. But Brown brushed off that worry. “Democrats win the argument by saying Republicans again are cutting taxes on the rich to deny Social Security beneficiaries the expanded Social Security they should get and have earned,” Brown said. “Most of us should be willing to make that argument.”

Indeed, the push to expand Social Security is emerging as another key issue — along with Wall Street accountability, stagnating wages, and the general sense that the gains of the recovery are going to the top — in the broader debate over whether the Democratic Party needs to move in a genuinely populist direction. But Brown conceded that may Dems are still unwilling to go there.

“Democrats aren’t always willing to lead on economic populism,” Brown said. “But it works everywhere, because that’s where the public is. It’s  a pretty populist public in terms of the minimum wage and social insurance generally.”

Greg Sargent writes The Plum Line blog, a reported opinion blog with a liberal slant -- what you might call “opinionated reporting” from the left.