NASHUA – Democratic presidential front-runners Joe Biden and Bernie Sanders continue their disagreements heading into the final days before the Iowa caucuses and the New Hampshire primary.

As Sanders pushes for a complete overhaul of health care in the form of a $20 trillion (or up to $40 trillion, as Biden says) Medicare for All strategy, Biden prefers a $750 billion “public option” expansion of Obamacare. Biden’s main gripes about Medicare for All seem to be that he believes it would cost too much and that it would eliminate the rights of individuals to keep private insurance, if they so choose.

Now, however, the two are squaring off on the issue of Social Security.

Last week, Biden stated via Twitter: “My administration will not cut Social Security or Medicare benefits. Period. We’ll expand them.”

On Monday, Sanders tweeted: “Seniors cannot live in dignity when they’re trying to survive on $13,000 or $14,000 a year in Social Security benefits. We have some bad news for those who want to cut Social Security. We’re not going to cut Social Security benefits. We’re going to expand them.”

However, as a congressman in the 1990s, Sanders expressed an openness to making “adjustments” to the tax and benefit structure of Social Security. He also praised an overhaul of the social safety net program signed into law by President Ronald Reagan that reduced benefits and increased taxes on working families.

Sanders’ presidential campaign and allies have highlighted similar remarks by Biden to attack the former vice president and make the explosive charge that Biden was an outspoken proponent of slashing the program.

Sanders, a democratic socialist, is a favorite of progressives who admire him for his convictions and consistency on issues. But when it comes to Social Security, it appears that wasn’t always the case.

In 1994, after Republicans took control of the House for the first time since the Eisenhower era, they brought a renewed focus on fiscal restraint and deficit reduction.

Biden and Sanders both bowed to those pressures in some respect.

Today, Social Security’s long-term finances are sagging under the weight of the ballooning number of baby boomers who are collecting benefits. The options available to sustain the program’s financing also remain the same: Benefits can be cut, taxes can be raised or a combination of the two can be enacted.

Sanders’ allies have specifically highlighted Biden’s past use of the term “adjustments” — a word they say was deployed as a euphemism for cuts.

Yet Sanders himself used the word in an election-year opinion article about Social Security that ran in The Burlington Free Press in 1996.

“As our population ages,” Sanders wrote, “it is clear that we will have to make incremental adjustments in Social Security taxes and benefits — as Congress has done in the past.”

During a 1999 press conference, Sanders went further, praising an overhaul of Social Security signed into law by Reagan in 1983. The legislation, which came as the program was on the brink of insolvency, raised taxes on working families, froze benefit increases for six months and gradually raised the age in which retirees can receive full benefits from 65 to 67.

Sanders said it was a good example of people coming together to enact a solution without draconian changes.

“We should remember that in 1982, Social Security was within a few months — a few months — of not being able to pay out all benefits owed to Americans,” Sanders said at the time. “And then people came together and said of course we want to save Social Security. They worked together, and they did.”

Sanders’ campaign disputed the idea that his remarks were a sign of approval for reduced Social Security benefits. They say he has a lengthy record of opposing cuts to the program and has instead supported tax increases or spending reductions to other programs, like military aid. They say the quotes, stripped of this broader context, present a deceptive version of Sanders’ actual beliefs.

That’s the same rebuttal Biden’s campaign has invoked in response to attacks by Sanders and his allies.

Recently, CNN unearthed a video of Sanders voicing his approval for a 1994 crime bill, which critics contend sparked an era of mass incarceration that disproportionately locked up black men.

Sanders has since said that he regrets voting for the “terrible” bill. But at the time, he praised it for striking a balance between making more money available for police and jails while funding crime prevention efforts.

Biden, who has been attacked over his vote for the bill, has also apologized for supporting the measure.

The back-and-forth with Sanders over Social Security highlights Biden’s evolution over a long public career, much of which was centered around his tenure as centrist senator and deal maker.

Biden’s campaign points to a long list of legislation he supported that increased Social Security benefits. But as an influential legislator who had a hand in passing major bills, he also was willing to enter negotiations with Republicans by considering a reduction in cost-of-living increases.

Often these changes were presented as a way to cut costs that would save the program.

As the Democratic Party moved leftward – a development that tracks along ever-widening income and wealth inequality – Biden has moved with it.

“There will be no compromise on Medicare and Social Security, period. That’s a promise,” Biden said on Jan. 20 at the Black & Brown Forum in Des Moines.

As Sanders, a Vermont senator, has risen in the polls, he and his allies have sought to turn Biden’s past remarks about Social Security against him. They’ve circulated video footage, news stories and transcripts of his past remarks. In some cases, what appears to be a sweeping statement by Biden lack crucial context.

One of the principal examples is a clip from a 2018 speech in which Biden discussed in favorable terms then-House Speaker Paul Ryan’s comments that a rising deficit demanded action on the popular entitlement programs. The video, circulated on Twitter by a top Sanders adviser, omits Biden’s larger criticism over how Ryan handled the 2017 tax cuts and subsequent budget debates.

Other widely distributed videos of Biden as a U.S. senator from Delaware in 1995 and presidential candidate in 2007 show him explaining his support for a more austere federal budget, including putting Social Security and Medicare “on the table.”

“When I argued that we should freeze federal spending, I meant Social Security, as well,” Biden said during a 1995 speech on the Senate floor. “I meant Medicare and Medicaid. I meant veterans’ benefits. … And I not only tried it once, I tried it twice, I tried it a third time and I tried it a fourth time.”