(Bloomberg) -- Richie McPhillips, living at the epicenter of the Brexit crisis, has a new worry -- Boris Johnson.

The favorite to succeed Theresa May as U.K. prime minister, Johnson said again on Wednesday he’s prepared to lead the nation out of the European Union without a deal if necessary, taking a harder line than most of his rivals. For McPhillips, that could mean a return to checkpoints and unrest along the Irish border that runs close to his home.

“Boris is a danger to the border,” said McPhillips, 61, who lives in Lisnaskea in Northern Ireland and voted against Brexit. “He would not bring any stability to the British political system.”

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The question of keeping the Irish border invisible has shaped the entire Brexit negotiation process, with the so-called backstop ultimately costing May her premiership. Johnson wants to renegotiate that part of the deal, which was designed to keep the frontier free of customs officers, police or soldiers.

All sides said they wanted to avoid a hard border emerging that could pose a threat to peace on the divided island. But the measure is loathed by Brexit-backers because it risks binding the whole U.K. to EU rules indefinitely.

In the past, the former foreign secretary has described the backstop as “a suicide vest around the British constitution,” and “a constitutional monstrosity” that no other nation would accept.

Johnson later voted for the backstop in Parliament at the third time of asking as he said he feared failing to do so would mean losing Brexit altogether.

Now, he’s holding out the prospect of a no-deal Brexit if Brussels refuses to redraft the divorce agreement. In London, as he launched his campaign to succeed May, Johnson dialed down his earlier rhetoric, saying he isn’t aiming for no-deal exit, but the U.K. must keep the option on the table. He’s vowed to leave the bloc on Oct. 31 no matter what.

Johnson, a key figure in the Brexit campaign of 2016, has suggested the congestion charges he oversaw as London mayor could be a model for solving the border conundrum, an idea Ireland’s Foreign Minister Simon Coveney has dismissed as “extraordinary.” The 310-mile frontier meanders through countryside, dividing rivers, fields and even some houses.

A spokesman for Johnson didn’t respond to a request for comment for this story.

Several rivals also want to renegotiate the deal, but shy away from Johnson’s rhetoric. Foreign Secretary Jeremy Hunt, the current second-favorite, has called a no-deal Brexit “political suicide.”

Others, such as former ministers Dominic Raab and Esther McVey have deployed even stronger no-deal rhetoric than Johnson, but without his profile and status, attract little attention along the border.

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Johnson does have some fans in Northern Ireland.

“I think he would make a good leader, I like his style, I like the way he conducts himself, ” said William Walker, 56, a local councilor for the Democratic Unionist Party, which backs Brexit. “I believe he is an honest man.”

“If Boris becomes prime minister, he should make sure we get out of Europe hopefully with a deal,” said Walker. “But if we leave without a deal, it will not be the end of the world.”

Ultimately, though, whoever becomes prime minister could find themselves boxed in on all sides, just as May has been. There’s no sign that Brussels is prepared to offer significant concessions. Walker’s DUP holds the balance of power at Westminster, and will keep fighting the backstop without those concessions. And there’s no majority in Parliament for no-deal.

“Personal charm and political skills won’t make much of a difference to the outcome in the short term at least -- it won’t change the arithmetic in Parliament,” said Richard Bullick, a former adviser to DUP party leader Arlene Foster. “There’s no majority for the current deal and no majority for no-deal. So we could be in for another extension.”

Even some Leave supporters in the region question whether Johnson can deliver Brexit, or any solution for the border.

“Boris wouldn’t be my first choice, no,” said Barry Read, 47, who lives near the border in Northern Ireland and voted for Brexit. “He has too much baggage. ”

--With assistance from Alex Morales.

To contact the reporters on this story: Dara Doyle in Dublin at ddoyle1@bloomberg.net;Rodney Edwards in London at redwards102@bloomberg.net

To contact the editors responsible for this story: Emma Ross-Thomas at erossthomas@bloomberg.net;Chad Thomas at cthomas16@bloomberg.net

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