I know, I know, I know. We have been here before, and on more than one occasion.
But senior Eurosceptics are more sure than ever that they have enough support to trigger a vote of no confidence in the prime minister. That doesn't mean it is bound to happen.
The last time they said so, and said so pretty publicly, their confidence was a mirage and the numbers did not emerge.
It became evident to ardent Brexiteers that their communications between each other were not all genuine, and painfully so. Those who had told colleagues that they had submitted the letters, patently had not done so.
What feels different tonight is that those who take this all extremely seriously, who had their hopes dashed the last time, are suggesting privately, not necessarily with glee, that they might have done it this time, and crucially if the list isn't long enough tonight, they have more MPs ready to join the calls.
Why now? Since yesterday's delay, the frenzy around here has turned to anger. Pushing the vote on the Brexit compromise back might have been politically logical, but it's driven Tory MPs crazy.
And not just on the Eurosceptic side. One former Remainer, who's been loyal to the PM so far, got in touch this morning to say they'd had enough and were putting their letter in, telling me what's happening right now is "disgraceful" and "it's just about saving her skin".
And another former Remainer has just told me if the prime minister doesn't have the courage to bring a vote to the Commons on her deal before Christmas, they will submit a letter too.
But, let's take a breath. There is of course, as you'll know if you read this blog often, no way right now of being sure how this will all play out. At 15.00 GMT I was pretty reliably told that the threshold for a contest hadn't been reached.
Two and half hours later, the prime minister herself said that she hadn't been told it had.
Remember, only one person really knows about the numbers, and that's Sir Graham Brady, the chair of the Tory Party's 1922 backbench committee.
It seems unlikely now that there will be any dramatic movement tonight. The prime minister will be back from Brussels late this evening and, will then, if the plans don't change, face MPs at Prime Minister's Questions, then hold Cabinet, then head to Dublin to try again to save her Brexit deal by seeking further movement from her EU counterparts.
But the threshold that would see that day interrupted by a challenge to her leadership may be reached, which would begin a formal process that might see her downfall, with a ballot perhaps on Monday. The rebels know of course, that the prime minister might win, leaving the Tory Party locked even more tightly into the mire.
If she survived the vote, the prime minister is then theoretically safe for a year. And even if her detractors were to win what is right now a theoretical contest, there is no straightforward solution for any potential new leader.
None of the rival Brexit tribes are big enough to get all of Westminster onside. It's still not the case there is an alternative plan that could get a majority in parliament.
And even if there was, it's not the case for the Tories that they could agree on the best person to put it forward. And Labour isn't ready yet to try to force a vote of confidence that might remove the government.
It's like this whole place is stuck in a trap where no one has an easy escape route at all, like the controversial backstop itself, no one on their own, can find a way out.
But it's possible that MPs on her own side are about to provide the prime minister with a forced exit.