That will bring every retiree into the streets....and they vote. Democrats know this would be the death knell for their party in future elections.
When the Dow goes from 16,000 to the 5,000 or so where it belongs, every retiree will come into the streets and vote - to be made whole. When the government promises to restore the nominal value of everyone's 401K to within 10% of its peak value as long as 80% of it is held in "safe, reliable" US Government securities, very few are going to shout "Thief!" and refuse to support the new plan.