Congressional liberals threatened to vote down whatever results from President Obama's fiscal commission if it contains a plan to change Social Security.

Liberal members of the House and Senate Democratic caucuses said they would look to defeat the fiscal commission's final proposal if it calls for cutting Social Security benefits, raising the retirement age, or privatizing any part of the entitlement program.

"[D]o not send Congress a plan that cuts Social Security benefits, raise the retirement age, or privatizes Social Security," Sen. Bernie SandersBernard (Bernie) SandersDems ponder gender politics of 2020 nominee 2020 Dem contenders travel to key primary states After Florida school shooting, vows for change but no clear path forward MORE (I-Vt.) warned Thursday on a conference call. "If you do, we'll vote it down."

The bipartisan commission Obama created by executive order is set to make its proposal to address the nation's looming debt crisis at the end of the year. House and Senate leaders have pledged to allow a vote on the entirety of the recommendations, which would come during a lame-duck session of Congress.

But both Republicans and Democrats have already been jockeying over the commission's final possible outcomes. GOP leaders have railed against the prospect of any new taxes, and Democrats have led the push to leave Social Security unchanged.

"This isn't just a political exercise," said Sen. Sherrod BrownSherrod Campbell BrownLawmaker interest in NAFTA intensifies amid Trump moves Dem senator shares photo praising LeBron James after Laura Ingraham attacks Trump gets recommendation for steep curbs on imported steel, risking trade war MORE (D-Ohio), who argued that working class citizens couldn't reasonably survive an older retirement age.

"This is something that I hope the Obama administration will join with us," added Rep. John Conyers (D-Mich.), the House Judiciary Committee chairman. "I think that that commission with all due respect to all of them should keep their paws off this subject matter."

The push also comes against the backdrop of November's looming elections. Democrats have accused Republicans of wanting to privatize Social Security.

GOP leaders haven't ruled out the idea of making changes to Social Security, but they also haven't openly embraced that notion after having been burned by it when President George W. Bush proposed reforms in 2005. 

House Minority Leader John BoehnerJohn Andrew BoehnerRestoring fiscal sanity requires bipartisan courage GOP congressman slams primary rival for Ryan donations Speculation swirls about Kevin McCarthy’s future MORE (R-Ohio), the would-be speaker in a GOP majority, said that lawmakers need to have an "adult conversation" about the looming fiscal crisis with Americans.