The Democratic budget, proposed by Budget Committee Chairwoman Patty MurrayPatty MurrayLawmakers send McCain well wishes after cancer diagnosis Trump labor board nominees advance in Senate Dems tout failure of GOP healthcare bill MORE (D-Wash.), has already come under heavy fire from Republicans who say it over-estimates the extent to which it would reduce the deficit, as well as raises $1 trillion in new taxes. Democrats say their budget cuts the deficit by $1.85 trillion over 10 years through an equal amount of spending cuts and new revenues, but the GOP has said that because the plan assumes the sequester will not happen, the amount of deficit reduction is closer to $700 billion.

The Democrats’ budget directs the Senate Finance Committee to find $975 billion in tax increases by closing tax loopholes for the wealthy and corporations. The resolution specifies that the taxes have to be progressive and not harm the middle class. But Rubio said he would still introduce at least two amendments.

Rubio said one of his amendments would not allow the Finance Committee to eliminate or raise the mortgage interest reduction tax — one of the largest tax expenditures. But Democrats have widely supported that tax deduction, so it would unlikely to be cut.

“Another thing, we shouldn’t raise taxes on the middle class at all to pay for more government, so I will offer an amendment on that as well,” Rubio said.

Under the budget proposal, Democrats use some of their $1 trillions in new tax revenue to replace sequester cuts and pay for $100 billion in stimulus. Democrats say the stimulus is necessary to help grow the economy and train the workforce.

The Democratic plan doesn’t reduce the overall government debt. Rubio said the debt is hurting the economy because people and businesses are fearful of another economic crisis.

“The debt is hurting us today,” Rubio said. “[People] believe unless this debt is solved we’re going to have a financial crisis in this country. ... So there are jobs that are not being created right now because of fear of the debt, and this budget doesn’t fix that.”

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.