About $1 trillion in new revenue would flow to the government over the coming decade - on top of more than $600 billion in taxes on upper-income earners approved in January - and would be coupled with a net $875 billion in spending cuts.
Those reductions would be generated by modest cuts to federal health care programs, domestic agencies and the Pentagon and reduced government borrowing costs. The budget proposes $100 billion in new spending for infrastructure projects and job training programs.
The president will reveal his own overdue tax-and-spending plan in two weeks, a plan that will be judged in part by whether it offers new, more politically risky proposals that could form the foundation for a bipartisan agreement between the two houses.
Senators braced for dozens of votes during a marathon session running late on Friday, with some predicting a final vote on the Democratic plan in the pre-dawn hours of Saturday.
In early voting Friday morning, Democrats rejected the latest attempt to repeal Obama's landmark health-care law by a strictly party-line vote.
The Senate has already taken several politically freighted votes, including a move by Democrats to force a vote on the Paul Ryan House budget, which was rejected by a 59-40 vote Thursday night, with five Republicans joining every Democratic senator in opposition.
Republicans countered with a move by Sen. Jeff Sessions (R., Ala.), putting Democrats on record in opposition to balancing the budget by the end of the decade. It failed on a near party-line vote.
Additional votes on Friday could feature forays into off-topics like supersized soft drinks, domestic drone strikes, handguns, and abortion - in addition to the more traditional subjects of taxes, spending, and debt.