Progressive activists fired a shot across the bow of congressional Democrats on Wednesday, warning them to protect Social Security, Medicare and Medicaid or face a primary challenge.

Adam Green, the co-founder of the Progressive Change Campaign Committee, said Democrats would face a "nuclear war on the left" if they supported cuts to the safety net programs.

"We will probably have a fractured party for the next two years" if Democrats cave to Republican demands, Green said on CSPAN, "which would be to the detriment of this president and very unfortunate. There will absolutely be Democratic primaries in the next round of congressional elections. We would probably start right away recruiting challengers."

He also criticized President Barack Obama for putting "chained CPI" on the negotiating table, a measure of inflation for Social Security that would lead to smaller cost-of-living increases for beneficiaries.

"We don't yearn for this nuclear war on the left," Green said. "It is really ironic for me, someone who woke up every day in 2008 and thought, 'What could I do today to get Barack Obama elected president,' to be having to fight a Democratic president on Social Security."

He noted the Progressive Change Campaign Committee had focused on congressional Democrats, and Elizabeth Warren in particular, during the 2012 elections. Green indicated he was already quite pleased with having Warren in the Senate, noting she recently slammed insurance giant AIG.

Watch video, courtesy of CSPAN, below: