They know they won’t succeed. Democrats, with 54 votes, have enough to pass anything that requires a simple majority, and won’t have much trouble getting to a filibuster-proof 60 votes, either. “I could count six or seven Republicans who would vote for full funding of the continuing resolution without breaking a sweat,” says one Senate aide who supports defunding. “So they’re going to get to 60.”

But that’s just the discretionary part of Obamacare. The far bigger portions of the program, including the billions and billions of dollars in subsidies that will start going to Americans on Jan. 1, are mandatory spending, an entitlement funded by an automatic appropriation which is written into law and runs without further congressional action. To change that, Congress would have to change Obamacare.

In the Senate, that would take 67 votes — the amount needed to overcome a guaranteed presidential veto. If the 46 Senate Republicans voted unanimously to end the Obamacare entitlement, they would have to persuade 21 Democrats to go along.

The Senate Republicans advocating defunding know that’s not going to happen.