Conservatives leading the fight to defund Obamacare in a must-pass budget bill are urging Senate Republicans to filibuster legislation that would do exactly that.

Senate Majority Leader Harry Reid, D-Nev., hasn't announced how he'll proceed on the House-passed continuing resolution to prevent an October government shutdown and defund Obamacare. But Capitol Hill observers expect Reid to strip out the provision defunding Obamacare, a move that would leave Senate Republicans no choice but to filibuster a measure some of them have been demanding.

Even supporters of the defunding effort are advocating that their counterparts in the Senate stall the House bill.

Their argument is that votes to begin and end debate on the House bill — which requires 60 votes — help Reid move the legislation through the parliamentary process to a point at which Democrats can sidestep the filibuster and strike the defunding provision with a simple majority vote. That would allow Democrats to advance the measure and ultimately pass it without Republican support.

“I hope that every Senate Republican will stand together and oppose cloture on the bill in order to keep the House bill intact and not let Harry Reid add Obamacare funding back in,” Sen. Ted Cruz, R-Texas, a vocal proponent of defunding, said.

It's not clear whether Senate Republicans can muster the 41 votes they need to prevent Democrats from advancing and amending the House bill. Most Senate Republicans oppose the defund-or-shut down strategy, and explaining to voters why they voted against a bill they originally demanded the House pass could be difficult.

Here is how the process could play out:

• Reid could take another House bill already on the Senate calendar, gut it and then add amendments that would effectively fund the government without defunding Obamacare. However, that would likely add an additional vote and two days of debate to a process already expected to last a week. It would also allow Republicans to filibuster a bill that does not defund Obamacare. For that reason, Reid is likely to stick with the House-passed budget bill.

• Conservatives who favor defunding said they will hold their fire and not try to block the bill when Reid brings it up for its first procedural vote – one that would allow debate to begin — next week. However, when lawmakers cast a second procedural vote on Sept. 28 to end debate and advance the bill for a final vote, Republicans said they will move to filibuster the measure, preventing a final vote. If they succeed, the government could run out of money and shut down on Oct. 1.

• If this filibuster fails, it would mean that enough Republicans voted with the Democrats to close off debate and Reid would likely call for a vote on an amendment that strips out the Obamacare provision. This vote would not be subject to a filibuster. It would pass the Democratic chamber and be followed by a final vote on the amended bill — probably on Sept. 29 — which is likely to pass.

Supporters of the defund-or-shut down strategy say they would drop their plans to filibuster their own bill if Reid allowed for a 60-vote threshold on the amendment stripping out Obamacare defunding, giving Republicans a chance to defeat it.

“We are not opposed to bringing the bill up. We are urging Republicans to oppose cloture on the bill unless Harry Reid agrees to either drop his amendment to fund Obamacare or agrees to make it a 60-vote question,” a committed defunder said. “Reid must not be allowed to fund Obamacare with only 51 votes.”