YORK, England — At this pivotal moment in Britain’s history, with the future of its economy and its place in the world soon to be determined, the leader of the country will be chosen next week not through a grand national election, but by mail-in ballots from about 160,000 members of the Conservative Party who paid their annual dues.

That’s not a thin slice of the population, it’s a crumb — about 0.25 percent of the 66 million people in the United Kingdom, or about 0.35 percent of the total electorate. 

And it’s an unrepresentative crumb, at that: dominated by white men who tend to be older and better off than your average Brit — and more insistent in their desire to leave the European Union.

“They’re consumed, if not obsessed, by Brexit,” said Tim Bale, a politics professor at Queen Mary University of London who has studied the party membership.

If the general public were voting, polls suggest they would prefer Jeremy Hunt, who as foreign secretary has supported Prime Minister Theresa May’s compromise vision of Brexit, to Boris Johnson, who headlined the winning Brexit referendum campaign in 2016. The most recent polls of Conservative Party members, however, favor Johnson over Hunt by more than 40 percentage points.

“Imagine you’re a soldier in battle,” suggested Paul Sullivan, 61, a local councilor who was hoisting a quick pint before the start of a campaign event here in northern England. “You go with the general who wants to win it, right? Or you’ll end up dead on the field.”

Johnson — a bombastic, erudite, crowd-pleasing former London mayor — has promised to either strike a fantastic new Brexit deal or leave the bloc without one by October. “Do or die,” he vows.

That goes over well here.

Many of those at the York convention hall resembled the Tory demographic. Silver-haired, wearing sensible shoes and “Back Boris” stickers, they were the sort that once ran small businesses, served as middle managers or were homemakers.

“I think of the hundreds of thousands, the millions of boys who died so we could be a nation,” said Brexit and Johnson supporter Carole Brown, 82. “And we’ve handed it over to Europe? Bring it back home, I say.”

This generation harbors lots of World War II nostalgia, even if some don’t recall Winston Churchill so much as movies about Churchill.

In addition to these elders, there were surprising numbers of teenagers in the hall in York. That’s another oddity of this contest: Children can vote. At least anyone 16 and older who is a member of the Conservative Party can. It costs $31 a year to join, or $6 for those under 23.

In York, the Tories liked the idea of “taking back control” from Brussels. And they liked Johnson’s sunny optimism. They said they had had enough of the sour May, whom they cast as a failure. And they agreed with the characterization of Hunt as “Theresa in trousers.”

When Johnson told the audience that what’s been lacking in Britain is “a bit more self-belief,” they harrumphed their support. They laughed when he said it was time to stop looking at Brexit “as a plague of boils,” but as an opportunity for Britain to shine.

When pressed by a moderator on how he would get Britain out of the E.U., Johnson didn’t really answer. He said that if the European leaders knew he was capable of leaving without a deal, they might very well give Britain what it wants.

“Boris has the charisma and the courage to see it through. Hunt is a very nice man but very ambiguous in his answers,” said Dani Marks, 62, a retired midwife, after hearing both speak.

“All politicians always have an exit clause. I’m not naive,” she said. “But Boris has nailed his foot to the plate on this. If he doesn’t deliver, his reputation would be shot.”

recent YouGov poll found that Conservative Party members would be willing to endure significant damage to the British economy (61 percent), the destruction of the Conservative Party (54 percent) and even the breaking up of the United Kingdom (63 percent) if it meant securing Brexit.

Surveys for the Economic and Social Research Council found that Brexit and the economy topped the Tory members’ concerns. Worries about the environment came in last.

“I favor leaving with no deal — the only way to really get all the way out,” said Alan Chapman, 76, who was in York to hear his man Johnson.

Chapman confessed he supported Britain joining the European Common Market back in the 1970s. But now? Shudders. By his account, the European Union has become an overreaching, supranational political colossus.

But might a no-deal Brexit be too much pain for too little gain?

Chapman, too, mentioned the Second World War. “It’s our generation’s turn to make its sacrifices now,” he said. “The Remain side is all about money, jobs, business, profits, greed, the economy. Remainers would sell their grandparents’ legacy for 20 pieces of silver.”

Johnson often talks about how today’s Conservative Party is a broad church. But it is a small parish, much diminished since the 1950s, when membership peaked at nearly 3 million.

John Major, a former Conservative prime minister who opposed Brexit and is backing Hunt, has noted how atypical Tory members are. The activists are “unrepresentative of the Conservative vote, let alone the interests of the country,” he told the BBC.

Major said national leaders should “look first at the interests of the country, not first at the interest of themselves and appealing to a particular part of a small electorate.”

Since May is being ousted by her own party rather than by a general election, the selection of her replacement at Downing Street is being overseen by the Conservative Party and governed by its rules.

Some members have mistakenly received more than one ballot, but party officials have urged them to vote only once.

It used to be that Conservative lawmakers in the House of Commons picked their party’s leader. Rule changes in 1998 instituted a two-phase process: the lawmakers whittle down the contenders and the membership decides between two finalists.

Twice under the new system, the Conservative Party wasn’t in power, so the winner didn’t become prime minister. And May avoided a vote from party members after challenger Andrea Leadsom dropped out of the contest.

So this will be the first time a prime minister is picked this way.

“It shouldn’t be that this narrow demographic group gets to decide the future of generations to come,” said Alex Runswick, director of the campaign group Unlock Democracy. She added that this “is a new constitutional precedent, and we are creating a new system without thinking it through.”

Adam reported from London.