In the Brexit twilight zone, words can mean one thing one day and something else the next. They can even mean two or three different things at the same time.

Take the deal that the U.K. and EU agreed two weeks ago. Boris Johnson says it will allow the country to "leave the EU’s Customs Union as one United Kingdom." But Democratic Unionist Party leader Arlene Foster argues it "will weaken the foundations of this great United Kingdom” because it creates a customs barrier between Northern Ireland and Great Britain. The deal's meaning depends on whom you speak to and where you sit.

Voters are used to taking political campaign pledges with a pinch of salt, but with Brexit set to dominate the run-up to the U.K.'s first December general election since 1923, candidates may find that skepticism on the doorstep is higher than ever.

And the moveable language on Brexit is not confined to the U.K. Despite cultivating an image as a bastion of consistency in the negotiations while repeating his warnings that "the clock is ticking," EU negotiator Michel Barnier has shifted his position on key points.

Here's POLITICO's guide to the slippery history of Brexit pledges.

'Do or die'

The claim: It was back in June during Johnson's campaign to lead the Conservative Party that he said in an interview with TalkRadio that the U.K. under his premiership would leave the EU "do or die" on the October 31. Since then he has repeated the pledge in numerous forms. In September he said on the steps of Downing Street that "There are no circumstances in which I will ask Brussels to delay. We are leaving on 31 October, no ifs or buts." And later that month he proclaimed he would rather be "dead in a ditch" than push back the Article 50 end date.

The outcome: Johnson did indeed ask for a delay — or was forced to by parliament. As a consequence, the U.K. is still in the EU on November 1 and will not be leaving the EU until next year at the earliest. The prime minister may yet have to face political mortality, but if so it will be at the ballot box in December. No drainage structures are likely to be involved.

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No renegotiation

The claim: Once the EU had reached a Brexit deal with Theresa May's government in November last year, Brussels was keen to signal to the U.K. parliament that this was the end of the negotiating road. This was the deal. Take it or leave it.

Even when MPs subsequently rejected the agreement by crushing margins in three votes, the repeated mantra from EU leaders and Brussels officials was that the heavyweight legal text of the deal — the Withdrawal Agreement — remained closed and could not be renegotiated. At the June European Council summit in Brussels, President Donald Tusk reiterated that no matter who was in charge in London, "nothing has changed when it comes to our position.”

He added: “the Withdrawal Agreement is not open for renegotiation.” And as recently as September, Barnier penned an article in the Sunday Telegraph telling the U.K. that the EU would not discuss alternative arrangements regarding the Irish border until the U.K. parliament ratified the unamended Withdrawal Agreement.

The outcome: The EU broke open their sacrosanct text and came to an agreement to expunge the backstop mechanism for avoiding a hard border on the island of Ireland, replacing it with a different plan.

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People's vote

The claim: The pro-EU Liberal Democrats spent months telling voters that they wanted to secure a referendum on the deal that emerged from the Brexit talks. Their leader Jo Swinson told a Remainer march in London in October: "We must secure a people’s vote and we must win a people’s vote.”

The outcome: When it became clear that the current parliament would not back a second referendum, the Lib Dems (along with the Scottish National Party) switched tack to backing a general election on December 9, outflanking Labour in the process. A cynic might observe that both parties were worried their electoral chances would take a dive if the poll happened after Brexit.

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Election now

The claim: Labour figures spent most of the Tory leadership contest earlier this year arguing that it was not democratic for 160,000 or so Tory members to decide the next prime minister. The winner should subject himself to the electorate in a general election. Labour leader Jeremy Corbyn reinforced the message in a letter to members in July. "We need a general election ... we need a Labour government to end austerity and rebuild our country for the many not the few," he wrote.

The outcome: But when he was offered an election by Johnson in September, Corbyn instructed his MPs not to back it, only changing his mind when he was bounced into it by the Lib Dems and SNP.

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'My deal or no deal'

The claim: Both sides in the talks have used the self-harm threat of a no-deal Brexit to their perceived advantage at one point or another. May hoped that fear of no deal would help get MPs skeptical of her deal on board with supporting it. She told the BBC in September last year, for example, that the alternative to her deal would be "not having a deal."

The outcome: The threat wasn't very effective with MPs, who never backed her deal in parliamentary votes. Barnier later revealed that May had "never" threatened the EU with a no-deal Brexit during the talks.

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'Row of the summer'

The claim: David Davis (remember him) in his role as the first Brexit secretary appeared to understand the strategic importance of the way the Brexit talks would be structured. When the EU insisted in 2017 on talking about the Brexit bill, citizens' rights and the Irish border in the first phase of talks — even though the latter was intimately tied up with the future relationship between the EU and U.K. — he said it would be the "row of the summer."

The outcome: Davis was right that this sequencing gave the EU negotiators a significant upper hand, but it was impossible to obscure his failure to change the format for the talks.

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I'm with the DUP

The claim: The hardest of hardcore Brexiteers have acquired the nickname "the Spartans" for their unstinting commitment to the cause of leaving the EU. But even they have shown a degree of flexibility and pragmatism. Jacob Rees-Mogg — then a Tory backbencher and now elevated by Johnson to leader of the House of Commons — pledged in March that he would reluctantly back May's deal if the Democratic Unionist Party came on board with it. That backing was despite his view that it was a "bad deal" that included "a £39 billion bill for nothing, a minimum of 21 months of vassalage, the continued involvement of the European Court [of Justice] and, worst of all, a backstop with no end date."

The outcome: At the third meaningful vote on the deal in March, the DUP stood firm and refused to support it but Rees-Mogg opted to troop through the government voting lobby anyway (along with one Boris Johnson). The vote was lost, but it was a foretaste for the DUP of how the Brexiteers would handle their input when Johnson was himself leading the negotiations.

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No customs border in the Irish Sea

The claim: As a backbench MP, Johnson went to the trouble of going to Belfast last year and giving a speech at the DUP's annual conference. He pledged not to "leave Northern Ireland behind as an economic semi-colony of the EU." And he said that separate arrangements in Northern Ireland "would be damaging the fabric of the Union with regulatory checks and even customs controls between Great Britain and Northern Ireland, on top of those extra regulatory checks down the Irish Sea that are already envisaged in the Withdrawal Agreement."

"No British Conservative government could or should sign up to any such arrangement," he added.

The outcome: Once he became prime minister and realized that the EU was never going to accept his plan of customs checks on either side of the border in Northern Ireland, his government made a last-minute pivot to a customs border down the Irish Sea. The DUP are not happy.

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Exploding UK

The claim: Prominent Tory Brexiteer Mark Francois said in September: "I think if we don't leave on 31st of October, this country will explode."

The outcome: The U.K. appears to be intact, although POLITICO was unable to verify whether Mr. Francois was still in one piece at time of going to press.

Emilio Casalicchio and Sanya Khetani-Shah contributed reporting.