Sen. Bernie SandersBernard (Bernie) SandersSunday shows preview: Lawmakers weigh in after Texas school shooting Voters Dems need aren't impressed by anti-waterboarding showboating Primary win gives resurgent left a new shot of adrenaline MORE (I-Vt.) marked the 79th anniversary of Social Security by vowing to fight any efforts to cut benefits.

“Social Security has been the most successful anti-poverty program in American history,” Sanders said. “We must oppose all efforts to cut Social Security and fight hard to expand it.”

When Social Security was first enacted in 1935, nearly half of U.S. seniors lived in poverty — now that number is only 9 percent.

Some Republicans have proposed privatizing the Social Security program or reducing the cost of living adjustments (COLAs) through a chained consumer price index because the Social Security Trust Fund has been operating at a deficit.

But Sanders, an ardent supporter of the program, frequently points out that Social Security hasn’t contributed a “dime” to the deficit. He calls it “the most successful federal program in modern American history.”

Sanders has said that if Republicans are worried about the solvency of the program — which has enough money to pay benefits for the next 19 years — they should agree to lift the payroll tax.

Currently, incomes more than $117,000 a year are not subject to the Social Security payroll tax so wealthier people contribute less of a percentage of their income than poor people. Sanders's bill would increase that income cap to $250,000 a year.