"If the Democratic Party is ever to regain the faith of ordinary Americans it must stand firm on the issue of Social Security," said Sen. Bernie Sanders.

Sen. Bernie Sanders (I-VT) opposes the bipartisan PROMISE Act, which seeks to fast-track the process to extend Social Security's solvency.

"If the Democratic Party is ever to regain the faith of ordinary Americans it must stand firm on the issue of Social Security," said Sen. Bernie Sanders.