LONDON — With Britain’s membership in the European Union on the line, campaigners from the prime minister on down blanketed the country Wednesday trying to convert the undecided on the final day before the crucial vote.

Outlining his vision of a future with Britain retaining its position in the 28-nation bloc, Prime Minister David Cameron bristled at the notion that the country would be headed in the wrong direction if the “remain” side prevailed in Thursday’s vote.

“We are not shackled to a corpse,” Cameron told the BBC. “You can see the European economy’s recovery. It’s the largest single market in the world.”

Pushing for a British exit, or Brexit, the most notable figure on the “leave” side, former London Mayor Boris Johnson, mugged for the cameras at the Billingsgate Fish Market in East London and pretended to kiss a fish – a not-so-subtle reminder that this is an island nation that takes great pride in its independence and self-assurance.

“It’s time to break away from the failing and dysfunctional EU system,” Johnson said. “It’s time to have a totally new relationship with our friends and partners across the Channel.”

Wednesday’s feverish campaigning took place even as mourners gathered in London and other world capitals to honor the memory of Jo Cox, the youthful pro-EU Labour Party lawmaker who was stabbed and shot to death last week in her Yorkshire constituency.

Speaking to a crowd of 9,000 in Trafalgar Square on what would have been Cox’s 42nd birthday, her husband, Brendan, said that Cox “feared the consequences of Europe dividing again” and urged people to follow her example.

The motive for the killing is unclear but the rare slaying of a politician cast a shadow over a divisive campaign that has been unusually heated, even by the lively standards of British politics.

Nigel Farage, the outspoken leader of the U.K. Independence Party, resisted fresh calls to apologize for a controversial poster showing hundreds of non-white migrants making their way across Europe alongside the words, “BREAKING POINT.”

The poster, labeled racist by opponents, was unveiled hours before Cox was killed.

“I apologize for the timing and I apologize for the fact that it was able to be used by those who wish us harm,” Farage said. “But I can’t apologize for the truth.”

“This was a photograph that all newspapers carried. It is an example of what is wrong inside the European Union,” he said.The reach of the EU into every aspect of life has made the issues at stake far more complex than in a general election. And while the vote is final – unlike in an election where the results can be reversed in the next term – it is not legally binding and Parliament would have to vote to repeal the law that brought Britain into the EU in the first place.