When last we checked in on Ted Cruz’s crusade to defund Obamacare, he was calling on Senate Democrats to refrain from passing any amendment to the House “CR” funding the government that would strip its defunding of Obamacare by a simple majority vote in the Senate. The idea is that if Dems allowed this amendment to be subject to a 60 vote threshold (Dems are going to amend the bill to take out the defunding, and kick it back to the House), Senate Republicans could then presumably filibuster it.

Alas for Ted Cruz, that isn’t going to happen. A Senate Democratic aide tells me there is no chance the amendment getting rid of Obamacare defunding will be subject to filibuster, meaning only a simple majority of Senators will have to pass it. Since Dems control 54 votes, that won’t be difficult.

This isn’t all that surprising; indeed most expected it to be the case. But it’s worth having it nailed down, because it again underscores the hopelessness of Cruz’s crusade, which has now run smack into the reality it was always bound to bump up against, which is that Democrats control the Senate and the White House and are not going to agree to defund Obamacare.

Now, it’s true Cruz will continue insisting that Senate Republicans filibuster the overall spending bill, on the grounds that Dems will amend it later to get rid of Obamacare defunding. But that will only add to the ludicrous nature of all this, since it amounts to Cruz insisting Republicans must block the very bill he himself asked House Republicans to send over. And it will likely fail in any case because plenty of Senate Republicans think the defund crusade is insane.

Cruz, having had his bluff called by House Republicans, is now under pressure to prove he can get enough support in the Senate to make the defund crusade work. He can’t, which is why he is now laying the groundwork to blame House Republicans yet again later for his own failure, by calling on them to pass measures funding the government piecemeal — sanz Obamacare funding — until Dems finally cave and agree to unwind Obama’s signature domestic accomplishment.

But that, too, is a nonstarter for House Republicans, one House GOP aide tells me. “There is no scenario where Congress is going to decide that this part of the government is open and that part of the government is closed,” the aide says.

Indeed, this House GOP aide mocked Cruz and company for trying to deflect blame yet again to House Republicans for the pending loss in a battle that Cruz himself asked for in requesting that House Republicans send over a CR defunding Obamacare.

“They’re reminiscent of the Cobra Kai team in Karate Kid, yelling, `Sweep the leg! Sweep the leg!’ because they are unwilling to get into a Karate fight of their own,” this House GOP aide said.

All of this leads to another question. If and when the amendment to defund Obamacare is stripped out of the spending bill and a clean CR is sent back to the House, can Republican leaders there point to the defeat in the Senate, argue the defund-Obamacare brigade had its shot and lost, and say they have no choice but to allow a  vote on funding the government at current sequester levels? (After all, this is what GOP leaders appear to want; instead they want to fight Obamacare around the debt limit.)

The House GOP aide refused to speculate, saying he would never count out the possibility of a Cruz victory.

“We will not presuppose their defeat,” the aide said of Senate conservatives, in a tone that just may have been tongue in cheek. “They’re gonna fight, and they’re gonna win. Right?”

Greg Sargent writes The Plum Line blog, a reported opinion blog with a liberal slant -- what you might call “opinionated reporting” from the left.