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In the Alice in Wonderland world of Brexit, where up is often down, reality can be hard to come by.

An early election is on the cards, surely spelling danger and opportunity in obvious ways for the two main parties.

Boris Johnson, who pledged to deliver Brexit "do or die" by the end of this month, will be nervous if he has failed to deliver on his pledge by the time of the election.

And Jeremy Corbyn, with Labour Remain grassroots, will want Brexit unresolved by the time of the election. That would allow him to pledge to deliver a soft Brexit or no Brexit at all.

Remember, however, that when Alice fell down the rabbit hole she wondered whether she would fall through Earth and find people on the other side walking with their heads downwards.

And so it could prove with the Brexit general election.

Could Mr Johnson, even though he leads the most pro-Brexit party in parliament, actually want to fight an election before Brexit has been delivered?

And could Mr Corbyn, even though he leads the party with the largest number of pro-Remain MPs, prefer to have Brexit done and dusted before an election?

Here are how the Alice in Wonderland election calculations work.

Some figures in Downing Street are spoiling for an election before Brexit. They calculate that Boris Johnson's success in negotiating a deal with the EU, which saw EU leaders cross a red line in amending core aspects of the withdrawal agreement, has shown beyond doubt that he is deadly serious about delivering Brexit.

Yes, these people admit, the prime minister will be thwarted in his "do or die" 31 October deadline. But that can be turned to his advantage. They say Parliament forced the Brexit delay, paving the way for a "people versus parliament" election.

What next in Brexit wonderland?

With Jeremy Corbyn, some Labour MPs in Leave areas who want a Brexit deal have been left with the impression that the Labour leader has some sympathy with their arguments.

If Brexit is unresolved at the time of the election, Corbyn will be in a tricky position as the party faces both ways during the campaign. It will have to craft a message for Brexiteers in the Midlands and the North while reaching out to Remainers in London.

But if Boris Johnson's Brexit deal has been ratified by the time of the election, Jeremy Corbyn could fashion a campaign that would unite his party and appeal to all parts of the country - Leave and Remain.

In such a scenario, expect the Labour leader to say that Johnson wants to turn Britain into Singapore-on-Thames with a slashing of workers' rights and environmental protections.

Corbyn could pledge that, as prime minister, he would use the talks on Britain's future relationship with the EU to reverse the "Trump style" Brexit negotiated by Boris Johnson.

As we are in Alice in Wonderland nothing is certain.

An election before Brexit is described by many senior Tories as supremely dangerous for Boris Johnson.

"Boris may be a great Brexiteer but if he hasn't delivered Brexit by the time of the election - over to Nigel Farage," a former minister says.

Corbyn aides insist he wants to go into the general election offering voters a chance to change the nature of Britain's actual departure from the EU. He wants to be able to tie down a customs union in the departure negotiations. Labour would then offer a referendum with its new deal as a "credible leave option" versus Remain on the ballot.

Britain's political leaders agree on one thing; the immediate next steps will be decided in Brussels, rather than Westminster, as the EU decides how to respond to the Brexit extensions.

For the moment Boris Johnson and Jeremy Corbyn are tumbling down the rabbit hole uncertain of the destination.

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