Senate Democratic leaders Monday were working to engineer a filibuster of Sen. Tom Coburn’s ethanol amendment.

The Oklahoma Republican hijacked the Senate floor last week in order to force a vote on his proposal to end a controversial ethanol tax subsidy.

Coburn filed to cut off debate on his amendment last week in an unusual move, without informing leaders and catching his opponents off guard.

It’s generally seen as the prerogative of the Majority Leader to set the schedule and file motions to end debate, or invoke cloture. But Members in both parties would likely have blocked Coburn from getting a vote if he didn’t employ the tactic.

Coburn had been cautiously optimistic that he could get the 60 votes he needed, but the Democratic whipping operation could doom his efforts.

“Yes, there’s a new controversial procedural tactic afoot,” Coburn spokesman John Hart said. “It’s called voting. If Democrat leaders want to protect a $6 billion tax break for Big Oil, they are welcome to do so.”

Meanwhile, Sens. Amy Klobuchar (D-Minn.) and John Thune (R-S.D.) introduced an alternative amendment backed by the ethanol industry that would eliminate the tax credit but plow most of the savings into other ethanol subsidies. Their amendment would cut the deficit by $1 billion.