Britain is almost guaranteed to face a general election before Christmas after Labour officially swung behind a snap poll.
Jeremy Corbyn - who blocked an election three times - announced the bombshell change to the shadow cabinet after deciding the risk of an immediate no-deal Brexit is now off the table.
Parliament could now be dissolved within days and Britain plunged into a countdown to the first December election since 1923. A new government would be returned just weeks before the new January 31 Brexit deadline.
Shadow Justice Secretary Richard Burgon declared "we believe we're going to win it" as he proclaimed: "We want to get Boris Johnson out by Christmas!"
But no matter what happens Boris Johnson won't be the shortest-serving PM in history - as he will have outlasted George Canning's 119 days in 1827.
The change comes at a crucial time as MPs vote tonight on a Bill by Boris Johnson to trigger a general election on December 12.
Crucially Labour have not yet explicitly confirmed that they will back the Bill, there are still wranglings over the date and Mr Corbyn faces an angry Labour revolt.
But even without Labour support, the Bill was already expected to pass due to some agreement between the Tories, Lib Dems and SNP.
If it is backed by Labour's leader, it will be almost impossible for the Bill to fail even if there is a huge Labour rebellion.
Dozens of Labour MPs could rebel if they are whipped to back an election. Some 38 voted directly against holding a general election last night.
And a string of prominent Tories were also furious at Boris Johnson's decision to push ahead with an election instead of trying to pass his Brexit deal in Parliament.
But if the Tory and Labour front benches were to unite in tonight's vote an election would be guaranteed.
Labour's decision came after months of internal wrangling in the party.
Jeremy Corbyn and his closest aides back an election. But many Labour MPs fear they’ll suffer at the ballot box for their Brexit stance - which involves first negotiating a deal but then having a referendum on it.
Crucially Labour had said it wouldn't back an election until no-deal Brexit is off the table.
Previously this meant delaying Brexit until January, which has now happened. But there was confusion as Mr Corbyn then said it included the threat of a no-deal Brexit in 2021 that's tied up in Boris Johnson's plans.
Mr Corbyn was also publicly sceptical ahead of time - saying a December 12 election could disenfranchise students at the end of term and "it will be dark before 4pm".
But he did signal Labour could back a December 9 election because it wouldn't disenfranchise students.
And Labour had faced being bounced into an election anyway after the SNP and Lib Dems agreed to back it.
The breakthrough came at today's meeting of the shadow cabinet at 9.30am.
According to a statement released by his office, Mr Corbyn told his top team: "I have consistently said that we are ready for an election and our support is subject to a No Deal Brexit being off the table.
"We have now heard from the EU that the extension of Article 50 to January 31 has been confirmed, so for the next three months, our condition of taking No Deal off the table has now been met.
"We will now launch the most ambitious and radical campaign for real change our country has ever seen."
Shadow Justice Secretary Richard Burgon told Sky News: "We've avoided a no deal Brexit. That's been taken off the table because the EU have extended the deadline to January 31.
"That means Boris Johnson, who is deeply untrustworthy, can't therefore push us out on a no-deal Brexit during a general election campaign.
"So Jeremy has made it clear, John McDonnell's made it clear, the team has decided we will be backing a general election because we can't leave these Tories in power any longer.
"They've done so much damage across the country in terms of austerity and public services, and we've got a manifesto of hope that will deliver a better society for everyone in our country.
"So we're up for the fight and we believe we're going to win it. We believe we can make Boris Johnson the shortest-serving Prime Minister."
How today is due to play out
What are MPs voting on today?
MPs are being asked to rush through a new law in the space of six hours that would force a general election in December.
Boris Johnson is putting forward a "one-line Bill" - a full law, but an ultra-short one - overriding the 2011 Fixed-Term Parliaments Act.
That'll mean the Prime Minister no longer has to secure a 'super-majority' of 434 MPs in order to force an election.
This legal change will mean Labour can no longer block an election, like they did the three previous times he asked for one (the most recent time was last night).
The first hurdle vote (known as 'second reading') will be held some time after 5pm. Amendments are then expected in a two-hour flurry before final votes after 7pm. The Bill would then go to the House of Lords.
In order the pass the Bill, Boris Johnson will need a 'simple majority' of at least half of MPs voting. That's, at most, 320 MPs.
Labour MP Stella Creasy hit out furiously at the tight timetable - which will also compress warring amendments into a single combined vote. MPs could still vote the timetable down, throwing the day into disarray.
When will a general election be held?
Boris Johnson wanted an election on Thursday 12 December. But the Lib Dems wanted Monday 9 December.
Reports suggested they would reach a compromise date in between.
Tory minister Brandon Lewis said December 9 is too early because Parliament would have to dissolve this week - in order to have a 25 working day countdown.
"That wouldn’t give us time to get this Bill through and a couple of small pieces of legislation we need to do including some budgetary issues for Northern Ireland," he said. "December 12 means we can dissolve next week and have time to get that legislation properly through Parliament."
Lib Dem MP Chuka Umunna said "we're not going to accept the 12th" but left the door open to a compromise in between. Labour's Barry Gardiner said December 9 "certainly would" be better than December 12.
Will the general election vote pass tonight?
If Labour back it, yes. Even if they don't it will probably pass, as long as the SNP and Lib Dems reach an agreement over a date.
Parliament has 288 Tory MPs, 35 SNP MPs and 19 Lib Dems - more than enough to get the 320 votes for a majority, even if 20 or so rebel.
That means Boris Johnson wouldn't need Labour or the other smaller parties like Plaid Cymru, Greens or Independents to get it through.
Many of the 21 expelled ex-Tories also backed an election on Monday night, including former Cabinet bigwigs David Gauke, Amber Rudd and Greg Clark.
So who'll vote against an election? On Monday night, only 70 MPs felt strongly enough to actively oppose one rather than abstaining (sitting out the vote).
They included 38 Labour MPs, 5 from The Independent Group for Change, 4 Plaid Cymru and 4 Independents.
The others were Lib Dems who'll now change their tune, but not all of them. Heidi Allen said: "As it stands, Parliament is not permitted to amend this bill today - that’s an executive power grab by any measure and I won’t support it."
And several Tories voiced their disquiet...
Are all Tories happy and in support?
No.
A string of Tories lashed out last night at the government for pushing ahead with an election - and canning Boris Johnson's Brexit deal until afterwards.
As it stands, the Withdrawal Agreement Bill has passed its first hurdle, is ready to be debated in Parliament, and the EU has given us plenty of time to pass it.
But it'll have to start from scratch with precious little time if Boris Johnson wins a December election. And if he loses it'll be canned completely.
Tory MP Simon Hoare fumed: "What are we to say to constituents about the fact we may be able to find time for a five to six-week general election campaign and then the rigmarole of forming a Government - and yet not for bringing back the withdrawal Bill?"
Tory MP Damian Green added: "The sensible course of action - which, frankly, voters on all sides would expect of us - is to [debate and pass the Brexit deal Bill]."
Tory Alex Chalk added: "Surely the proportionate and sensible thing is to offer the House more time. If it does not vote for it, the Government will take their course, but surely they should at least try."
Will there be amendments?
There can be but they'll be rushed and could be ruled out of scope for the Bill.
Some will want to add radical changes like votes for EU citizens in the UK (currently barred from general elections) or votes for 16-year-olds.
But it's not clear this will pass because the Lib Dems - despite backing these reforms - suggested they'll abstain in the name of getting an election passed quickly.
A Lib Dem source said: "Let's be frank about the politics of this. If there are those kinds of amendments to this Bill, it doesn't go through."
What does this mean for Boris Johnson’s Brexit deal?
The deal is still active and agreed with the EU.
But the Bill that puts it into law (which passed an initial vote last week) will be parked until after an election, when it'd have to be brought back from scratch.
It'll be easy to bring back and pass if Boris Johnson wins a majority, and if he doesn't get a majority it's a different story. So the PM is gambling it all on winning the house.
Ex-Chancellor Philip Hammond - who was booted out of the Tories - raged at the decision to drop the Bill in favour of an election.
He said: "The idea that now we would use our precious time to halt all of this process for five or six weeks and go out and have a general election frankly appals me.
"I think the Government is trying to create a narrative that Parliament is blocking Brexit and therefore we need an election. But that is simply untrue."
