LONDON — British Remainers have a spring in their step.

While undoing Brexit altogether looks almost as unlikely today as it did in the immediate aftermath of the referendum last year, those who think Britain might be better off staying in the European Union are becoming more vocal as the complexities and potential costs of Brexit become clearer.

Vince Cable — who was crowned leader of the Liberal Democrats unopposed Thursday — has never supported leaving the bloc and is "beginning to think Brexit may never happen." Former U.K. Prime Minister Tony Blair last weekend suggested the U.K. could stay in a reformed European Union. Even the director of the Vote Leave campaign, Dominic Cummings, admitted on Twitter this week that there are “some possible branches of the future” in which “leaving will be an error.”

Donald Tusk, the former Polish prime minister and European Council president, put it more poetically last month. “You may say I am a dreamer. But I am not the only one,” he said, channelling John Lennon.

In Westminster, anti-Brexit dreamers are scarce but POLITICO spoke to some of those who believe Brexit could yet be halted. The political odds might be stacked against them, but then very few correctly predicted the referendum vote in the first place.

Here are nine scenarios in which Britain stays in the European Union:

1. Public opinion changes

Remainers have been heartened by a number of polls since the June 8 election which have suggested an uptick in support for staying in the European Union, including one by Survation that found 54 percent of Brits would now prefer to remain in the bloc.

However Joe Twyman, head of political and social research at YouGov, which has been monitoring public opinion since the referendum, said the shifts in views had been too small to point of a definitive change of heart. He said the country was still divided down the middle, much as it was in the referendum vote itself but added that "things could change massively."

"It is almost certain that as things do actually start to occur then there could be a movement in one way or another. People could say 'this is working out really well, yay us.' And so support for Brexit rises significantly. The opposite could be true if things go wrong."

The main political parties are all monitoring the situation through private polling, according to Twyman. The "smart ones" understand the fluid nature of [public opinion] and are aware that polls could change significantly.

It would be problematic for a government to force through Brexit — and especially a hard break with the EU — if the majority of Brits opposed the idea. The path to Brexit is a long one — public opinion is something neither side can take for granted.

Former Brexit minister and enthusiastic Brexiteer David Jones doubts public opinion has shifted. He points to the 85 percent of the electorate who voted in the election for parties committed to taking Britain out of the EU in June's general election.

2. Article 50 is revoked

European Commission officials insisted in a fact sheet issued in July that, once triggered, Article 50 cannot be “unilaterally reversed.”

But former diplomat Lord Kerr, who authored the clause, disagrees. At the time it was written he questioned whether a sub-clause was needed to clarify how a country could change its mind, but was told that if it did not say you can't take it back, you could reverse Article 50.

Another route to Britain staying in the European Union could also be through an extension of the two-year negotiation period allowed for in the article. While it is unlikely Britain would be allowed to extend the negotiation to try and get a better deal, Kerr believes more time could be granted so the public could be consulted further.

"Democracies cannot say no to a democracy being democratic. So they would say 'okay, how long would it take you?' I envisage it would take six to nine months and I think we would get that," he said.

Charles Grant, director of the Centre for European Reform, agreed. "The political imperative of keeping the Brits in the club would override any legal concerns," he said.

But one senior EU diplomat said he thought it unlikely leaders would agree to prolong the two-year deadline because it would mean "adding more uncertainty."

The EU wants to avoid creating a model for other European countries tempted to leave the EU.

3. Another election ... and then a referendum

"Not another one," Brenda from Bristol told the BBC when Theresa May announced she was calling a snap election. But one would be needed to stop Brexit.

"I think [public opinion] will turn as the economic arguments kick in. I would expect that by this time next year, the government will be coming back from Brussels with the outline of a rather bad deal, against a background of a public opinion that now thinks this isn’t necessarily a very good idea," said Kerr. "I would expect that deal not to carry in the House of Commons and there then [would have] to be an election."

Kerr thinks an election would lead to the EU granting an extension of the Article 50 timscale and it was "perfectly possible" there would a referendum in the first half of 2019.

Jones agrees that a general election would be needed to change the U.K.'s Brexit stance, but he can't see it happening.

“That would mean that you’d have to have a majority of two-thirds in the Commons in favor of an election," the former Brexit minister said. "You’d have to persuade a lot of Conservative MPs that it was in their political interest and in the country’s national interest to have that election. And the country would have to change its mind, and frankly all the polls one sees, if anything show there is a strengthening position of those who just want us to get on with Brexit."

4. Remainers find their voice

Gina Miller, the campaigner behind the Supreme Court case that forced Theresa May to get parliamentary approval for triggering Article 50, said Britain needed to stop its "collective irrationality" and have a proper debate about the consequences of Brexit.

“The politicians are in a cowardly environment where there is this vacuous populist will of the people that has been constructed. Unless the will of the people changes, I don’t think the politicians will have the courage to stand up and fight for our country, and that is a dismal state of affairs for the politics of our country to be in,” she said.

Miller believes a strong Remain vote in parliament could stop Brexit. "We have got a long way to go, but I don’t see it as being totally impossible as nobody can predict the future," she said.

Writing for his local paper, Blairite Labour backbench MP Ben Bradshaw agreed the debate was shifting.

"I've always thought there was a good chance Brexit wouldn't happen once the British people were faced with a terrible negotiation and an even worse deal. But the general election and its aftermath have brought that moment forward," he said.

"Only now are we having the debate about what Brexit actually means and the different types of Brexit that we didn't during the referendum campaign," he added.

5. EU reform

Blair's recent comment that the U.K. should consider staying in a reformed EU has puzzled some diplomats in Brussels.

The senior EU diplomat said the EU’s big plans for the future include more independence for the eurozone and the creation of an area of cooperation on legal matters. So “the future Europe will pull away from what the British people were looking for,” he said. “The reforms will go in the opposite direction, and we are not going to limit the scope of freedoms in the EU.”

The U.K has traditionally opposed efforts to enhance integration in the EU and did not support any effort to make the eurozone more self-reliant.

If there’s a new referendum on British membership within the two-year Article 50 deadline, and if British people elected a new pro-Remain government, “maybe we can think of it,” the diplomat said.

6. Labour Party

Charles Grant believes the Labour Party would have to commit to taking Britain back into the European Union if Brexit is to be halted — something Corbyn has shown little commitment to thus far.

Former MP Douglas Carswell, a leading campaigner for Vote Leave, dismissed the idea Corbyn would adopt the Blairite position and highlighted Corbyn's historic Euroskepticism.

"I probably knew [Corbyn] better than most Labour MPs when I was a Tory backbencher because every time we organized a Tory rebellion on Europe he joined us in the lobbies. His instincts are to see Brussels for what it is — a scam against working people."

Kerr acknowledges Corbyn's previous opposition to what he perceived as a "capitalist club," but thought pressure from public opinion and from the unions could shift Labour's position.

"If the TUC [Trades Union Congress] come out saying they are very nervous of leaving the EU because they don’t think the rights of workers and social policy and environmental policy will be as good when it is left to Tory free-market government, I would expect him to listen to that," he said.

7. Lib Dems gain ground

Liberal Democrats hoped that their offer of a second referendum on the final Brexit deal would bring them electoral success in the June election by hoovering up disgruntled Remain voters.

It didn't happen — they won just 12 seats. But Cable looks set to hold the line on the promise of a second referendum after taking over the party on Thursday.

Liberal Democrat Brexit spokesperson Tom Brake said the "huge challenges" Brexit will throw up were now becoming apparent and the party continues to believe that "no deal will be better than what we currently enjoy as members of the EU."

“That is why we will carry on fighting to give the British people the final say on the deal, with the option to reject the deal on offer and remain in the EU," he said.

8. Tory wars

A cabinet minister anonymously claimed in the Telegraph that Chancellor Philip Hammond is deliberately working to "frustrate" Brexit and treating pro-Leave ministers like "pirates who have taken him prisoner."

But even Remain supporters in the Conservative Party acknowledge Brexit will happen.

Nicky Morgan, now chairperson of the treasury select committee, said: "Come 2019 we will not be members of the EU."

She said it would only be stopped by "some seismic world event" where people said they "didn't want the government thinking about negotiations, and instead thinking about safety or foreign policy, whatever it might be."

It was important the triggering of Article 50 happened before the anniversary of the referendum because otherwise people would have said "there you go, the Westminster elite are not listening, they are ignoring and they are not doing what we voted for."

"That would be a disaster. The only people who would benefit from that would be Nigel Farage and his troops," she said.

9. Rejoin at a later date

Britain could apply to rejoin the European Union after it has left — but on what terms?

Grant said: "Once it has left, it could reapply to join like any other non-EU country in Europe. The negotiations would take several years and the U.K. would probably not be able to regain the special position it currently enjoys — with a rebate on its budget contribution and opt-outs from many policies."

“Once they’re gone, they’re gone,” the senior EU diplomat told POLITICO. “If they want to join again, they will join as another country would,” he added. “There won’t be any rebates, or opt-outs.”