Five Republican senators jumped ship and voted against House Republicans' 2012 budget on Wednesday.

Sen. Lisa Murkowski (R-Alaska) joined four other Republican senators who'd previously announced their opposition to the budget, which has sustained withering criticism by Democrats who say it would end Medicare as Americans currently know it.

Sens. Scott Brown (R-Mass.), Susan Collins (R-Maine) and Olympia Snowe (R-Maine) voted against it as they'd previously said they would, largely because of the reforms contained within the budget to Medicare, transforming it into a voucher-based system for Americans under the age of 55.

Also as expected, Sen. Rand Paul (R-Ky.) voted against the plan because he views it as not going far enough.

The budget, crafted by Rep. Paul Ryan (R-Wis.), had been the subject of scrutiny from Democrats, who credited its Medicare provision for a victory on Tuesday night in a special election to an upstate New York congressional district.

The underlying bill failed in a 40-57 vote, with 60 votes being needed to bring up the Ryan budget for debate. Two Republican senators did not vote.