Boxer criticized Ryan’s budget because it would change Medicare into a voucher system in order to save money.

“Let me know tell you about the Republican budget, if you are 55 instead of getting the same Medicare your parents got … it’s over, you will get a voucher,” Boxer said. “They say take that voucher and go find your own insurance. … Studies show you will be spending $6,000 more out of pocket for your insurance.”

Boxer said that because younger people would be taken out of the Medicare system, the remaining seniors would receive worse care because lawmakers would stop working to improve a “dying program.”

“This is a giant nightmare,” Boxer said. “These are suppose the be the golden years. The people who will lose this will have lost the golden Medicare guarantee. 

“If you end Medicare and destroy it like [Republicans] do, the people left in it are part of a dying program. Who is going to try to fix that dying program? … No one, there is no more Medicare.”

But Republicans have criticized the Democrats’ budget proposal for not doing enough to address entitlement spending — the largest government expense.

Sen. John ThuneJohn Randolph ThuneGun proposal picks up GOP support Overnight Regulation: Senate panel approves driverless car bill | House bill to change joint-employer rule advances | Treasury to withdraw proposed estate tax rule | Feds delaying Obama methane leak rule Dems see Trump as potential ally on gun reform MORE (D-S.D.) said the budget offered by Senate Budget Committee Chairwoman Patty MurrayPatricia (Patty) Lynn MurrayChildren’s health-care bill faces new obstacles Overnight Health Care: Schumer calls for tying ObamaCare fix to children's health insurance | Puerto Rico's water woes worsen | Dems plead for nursing home residents' right to sue Schumer calls for attaching ObamaCare fix to children's health insurance MORE (D-Wash.) does nothing to reduce entitlement spending.

“How are you going to fund the other priorities of the federal government when 90 cents of every dollar are being spent on these programs?” Thune said. “And this budget does nothing.”

Democrats say their budget cuts the deficit by $1.85 trillion over 10 years through an equal amount of spending cuts and new revenue, but the GOP has said that because it assumes the sequester will not happen, the amount if deficit reduction is closer to $700 billion. Republicans have said that in order to get a budget agreement in conference committee between the House and Senate, entitlement reforms will need to be included. 

“Social Security is already operating at a cash deficit. Medicare is going to be bankrupt 10 years from now. It’s clear these things are looking us right in the face,” Thune said. “These are issues today that need to be dealt with. … What are we going to do to save Medicare, Medicaid and Social Security?”

Ryan’s budget also doesn’t address Social Security.

The Senate will continue debate on the budget until Friday, unless time is yielded back. Then it will have a "vote-a-rama" on an unlimited number of germane amendments.