Senate Majority Leader Harry ReidHarry ReidChris Murphy’s profile rises with gun tragedies Republicans are headed for a disappointing end to their year in power Obama's HHS secretary could testify in Menendez trial MORE (D-Nev.) opened the Senate on Monday with a fierce attack on the House Republican budget, which the upper chamber is scheduled to take up later this week.

Reid ripped the GOP budget for its proposed reforms to Medicare, which Democrats for weeks have been criticizing.

“The Republican plan would shatter a cornerstone of our society and break a promise to our elderly and to our sick,“ Reid said. “People are talking a lot about that plan because there is a lot to fear ... It’s a bad deal all around.”

The GOP plan, crafted by House Budget Committee Chairman Paul RyanPaul RyanThe Hill Interview: Budget Chair Black sticks around for now Gun proposal picks up GOP support GOP lawmaker Tim Murphy to retire at end of term MORE (R-Wis.), would cut $5.8 trillion in spending over 10 years and transform Medicare into a sort of voucher system. It would balance the budget by 2040 without raising taxes. 

The budget proposal passed the House in March in a 235-193 with no Democratic support.

Only four Republicans voted against the measure in the House, but Sen. Scott Brown (R-Mass.) on Monday became the second Republican senator to say he would not support it.

That opposition, along with comments from former Speaker Newt Gingrich (R-Ga.), who described the reforms as right-wing social engineering, has emboldened Democrats.

“It's easy to see why the American people don't support it,” said Reid. “Democrats, Republicans and independents do not support the plan to kill Medicare or change it as we know it.”