Assisted dying reforms will either be a step closer to become law or crushed for a decade within 24 hours.
But the crucial result is on a knife edge as so many MPs are yet to decide which way to vote – or whether to even turn up at all.
Former prime minister David Cameron became the latest political big beast to announce he was in favour of the bill, but he does not have a vote.
Instead, 639 MPs will have the opportunity to back or oppose the legislation when it faces its first major parliamentary hurdle on Friday.
After a flurry of MPs revealing they would oppose it following Health Secretary Wes Streeting’s announcement he was against the plan, it appeared support was draining away.
But analysis by a number of news organisations now shows supporters in the majority, including from ITV News, which believes 196 MPs will vote in favour compared to 147 against.
Crucially, however, as many as 150 MPs are still wrestling with what to do, according to some tallies while around 25 are expected to abstain.
It means the result is still too close to call as the undecideds could swing it, even just by failing to turn up at all.