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The political fight to increase Social Security benefits passed a milestone late Thursday night as 42 Democratic U.S. senators voted to increase payments to beneficiaries and all Republican senators voted no.

While the amendment by Sen. Elizabeth Warren, D-MA, did not pass—nor did scores of others proposed by Senate Democrats as the body took up the 2016 federal budget—the roll call vote is a sign that expanding Social Security, whose payments to retirees now average $1,310 a month, is ascendant and will be in play in 2016.

Longtime advocates for expanded benefits commented privately online that the vote would have been unimaginable five years ago, when the conventional political narrative surrounding Social Security was that it, along with Medicare (healthcare for seniors), was causing the federal debt to grow too large and all benefits had to be cut.

Social Security and Medicare are the two largest government programs for seniors. However, the way they are financed differs greatly. Social Security is financed through payroll tax deductions on the first $118,500 of income. By law, all of the benefits have to come from the money the government holds in its trust accounts.

Federal analysts have predicted that the Baby Boom generation will require that more money be added to these accounts by 2033 or else benefits might have be cut by about 20 percent of what is now projected for retirees. The defeated Senate amendment would have created a "deficit-neutral reserve fund" to begin to shore up those reserves.

Advocates for expanding Social Security have said that payments today are not enough for the roughly 20 million retirees who receive more than half of their monthly income from Social Security benefits. They have proposed lifting the income tax cap as the simplest and fairest way to expand near-term payments and to build up long-term reserves.

The political value of last night's roll call vote is that it signals the framing of the Social Security debate has changed and creates a clear record that will be used in the 2016 political campaigns.

There are other reverberations as well. With this morning's announcement by Senate Democratic Leader Harry Reid that he will not seek re-election next year, liberal groups are saying that Senator Warren should become the next Senate Democratic leader.

Steven Rosenfeld covers national political issues for AlterNet, including America's retirement crisis, democracy and voting rights, and campaigns and elections. He is the author of "Count My Vote: A Citizen's Guide to Voting" (AlterNet Books, 2008).