Majority Leader John Thune (R-South Dakota) conceded early Tuesday that he did not know if he had the votes yet to pass the measure.

With Sens. Rand Paul and Thom Tillis opposed to the package, GOP leaders can afford only one more defection. And multiple Republicans aren't yet sold on the measure.

The Senate slogged through a tense overnight session that has now dragged into Tuesday morning, with Republican leaders searching for ways to secure support for President Donald Trump’s big bill of tax breaks and spending cuts while fending off proposed amendments,