As Senate Republicans worked Thursday to push the fiscal year 2018 budget over the finish line to begin work on tax reform, Democrats forced them to take awkward votes on the debt, tax cuts for the middle class, and the Congressional Budget Office.

Passing the budget would allow Republicans to pursue tax reform legislation through the reconciliation process, sidestepping the Democratic filibuster. But they couldn't stop Democrats from forcing amendment votes.

Mark Warner of Virginia offered an amendment that would require tax cuts to be offset elsewhere in the budget with tax hikes or spending cuts.

Tammy Baldwin of Wisconsin and Ben Cardin of Maryland required votes on measures that would have required a 60-vote threshold for tax legislation that added to the deficit.

And Tim Kaine of Virginia did the same for requiring that the tax bill, or any significant amendments, get an official score from the Congressional Budget Office that is available for at least 28 hours beforehand.

The GOP blocked those amendments on party-line votes.

More uncomfortably, Republicans voted together to stop an amendment from Heidi Heitkamp of North Dakota, one of the more centrist Democrats, that would have required a 60-vote threshold for any tax bill that raised taxes on anyone earning less than $250,000.

While Republicans say their tax bill is meant to provide a middle-class tax cut, they viewed that amendment as a threat because it could create uncertainty about any reform bill. Wyoming's Mike Enzi, the Budget Committee chairman, called it a "poison pill" that would tie the Finance Committee's hands in writing the tax bill.

Maria Cantwell tried to take out the provision in the budget that could allow Republicans to pursue opening up the Arctic to drilling.

The Arctic National Wildlife Refuge is "one of the most pristine areas of the United States and we have been protecting it for decades for a reason," the Washington senator said. "The notion that we, tonight, after 60-plus years, would give up what is a biologically important area ... for what? For oil that we don't need."

The chairman of the Energy Committee, however, Alaska's Lisa Murkowski, defended drilling in her home state.

"We can and we must do more as a nation to responsibly develop our resources, our energy resources," she said.