By Mark Miller

CHICAGO (Reuters) – The future of Social Security is on the ballot this year – not that you could tell by the U.S. presidential debates, or by any other aspect of this rancorous, sensational election.

But 67 percent of registered voters rank Social Security as a “very important” part of their voting decision this year – just behind the economy, terrorism, gun policy and immigration, according to the Pew Research Center.

And so it should be. Social Security is the most important retirement benefit for most American workers – it provides at least half of the income for 48 percent of retired couples, and for 71 percent of single seniors, according to the Social Security Administration. Also, Social Security benefits kept 22.1 million seniors, working-age adults and children out of poverty in 2015 according to an analysis of Census data released this week by the Center on Budget and Policy Priorities.

But Social Security’s retirement and disability trust funds are forecast to be depleted in 2034. At that point, benefits would be cut an estimated 21 percent, unless Congress takes action.

Meanwhile, a consensus is developing that an expansion of Social Security benefits should be added to the reform agenda to address our growing retirement security crisis. Solvency and expansion can both be addressed by raising new revenue. Options include raising the cap on income subject to payroll taxes, raising payroll tax rates very gradually over a 10-year period or even allowing Social Security to invest a portion of the trust fund in equities.

Democratic nominee Hillary Clinton and Republican rival Donald Trump faced just one question about Social Security during their recent debates – and the framing was wrong.

Moderator Chris Wallace of Fox News asked the candidates how they would reform the program in light of its role as a key driver of the nation’s debt. Wallace had it backwards – Social Security actually lends money to the federal government, not the other way around.

Surplus trust fund assets are invested in a special type of Treasury note backed by the government’s full faith and credit. So Social Security is no more a driver of the debt than other holders of government bonds (China comes to mind). The Social Security trust fund is a lender to a government that spends much more than it levies in taxes. When the trust fund runs dry in 2034, there is no mechanism available to make up the funding gap from general revenue.

Wallace asked if Trump would make a deal to save Social Security (and Medicare) that included both tax increases and benefit cuts. Trump did not answer, instead pivoting to a critique of the Patient Protection and Affordable Care Act. Clinton, focusing on Social Security, reiterated her support for raising revenue through higher payroll taxes on the wealthy, fighting any benefit cuts and supporting targeted increases for low-income workers and women.

Her response is in line with what voters want. Another Pew poll, conducted back in March, found that 71 percent of registered voters oppose benefit cuts. That figure does not change much when you filter respondents by party affiliation or which candidates they supported in the primaries. Other polling suggests a majority of Americans would favor higher payroll taxes – on the wealthy or on themselves – to support the program.

Aside from the two candidates, where would the two major political parties take us on Social Security reform after the Nov. 8 election? The party platforms adopted at this year’s conventions are instructive.

The Republican platform states that solvency should be restored without tax increases. That is a de facto call for benefit cuts, because there are only two ways to solve Social Security’s financial problems: either you cut benefits or increase revenue.

The platform also states that Republicans “believe in the power of markets to create wealth and to help secure the future of our Social Security system.” That is a clear call for shifting Social Security to a system of private accounts, as advocated by President George W. Bush in 2005.

Meanwhile, the Democratic platform says this: ”We will fight every effort to cut, privatize, or weaken Social Security, including attempts to raise the retirement age, diminish benefits by cutting cost-of-living adjustments, or reducing earned benefits.” The platform document goes on to call for benefit expansion, at least for “women who are widowed or took time out of the workforce to care for their children, aging parents, or ailing family members.”

It also calls for “exploration of alternatives” to Social Security’s current annual cost-of-living adjustment that would be more “equitable” for seniors.

What might happen if Clinton wins, as expected? Odds are good that she would tackle Social Security reform sometime in a first or second term, but much will depend on which party controls the two chambers of Congress. Republicans can be expected to continue their push for a higher retirement age, less generous cost-of-living adjustments and some form of means-tested benefits. Democratic control of the Senate and House of Representatives would create a historic opportunity for legislative reform to restore Social Security’s long-range solvency and expand benefits.

If the Democrats fall short of that, their challenge will be to keep the debate about Social Security reform separate from phony debt arguments, and away from back room deals that do not require legislators to go on the record in favor of cutting, sustaining or expanding Social Security. In that scenario, lawmakers would have to explain to voters why they oppose putting some extra benefits in their pockets. Or, worse – why they are OK with allowing Social Security to keep veering toward a huge benefit cut in 2034?

The polling data tells us that expansion will win. Not that you could tell it in this particular election season.

(The writer is a Reuters columnist. The opinions expressed are his own)

(Editing by Matthew Lewis)

Photo: A voter holds his sample ballot as he works to cast his ballot during early voting at the Beatties Ford Library in Charlotte, North Carolina, October 20, 2016. REUTERS/Chris Keane