British PM race top contender, Boris Johnson

The contest to replace British Prime Minister Theresa May is due to narrow on Thursday when Conservative Party lawmakers vote to knock out at least one of the 10 candidates in the first ballot.

Although Boris Johnson is far ahead of others in the race, the United Kingdom could be heading towards a constitutional crisis over Brexit as many of the candidates vying to succeed May are prepared to leave the European Union (EU) on October 31 without a deal.

Nearly three years since the UK voted 52%-48% to leave the EU, the ruling Conservative Party had its worst result in centuries in a European election last month and opinion polls indicate that a snap election would produce a hung parliament.

The Conservative lawmakers would cast their votes in booths in a room in the British parliament on Thursday and any candidate with 16 votes less would be automatically  eliminated. If all candidates have more than 16 votes, the one with the least votes is eliminated.

The second round is due on June 18 with further ballots planned for June 19 and June 20 until there are just two candidates. A postal ballot of the wider Conservative Party membership will then be held to pick a leader.

Johnson, who led the official campaign to leave the EU in the 2016 referendum is the front runner to replace May despite a long record of scandals and gaffes. His closest rivals are Jeremy Hunt, the current Foreign Minister and Andrea Leadsom, the former Leader of the House of Commons

Of the 313 Conservative Party lawmakers, 81 have publicly backed Johnson, 32 have publicly backed Michael Gove, the Environment Minister and 30 have publicly backed Hunt.

Johnson kicked off his official campaign on Wednesday with a pledge to lead Britain out of the European Union on October 31 and a warning to his divided Conservative Party that any delay would mean defeat.

“After three years and two missed deadlines, we must leave the EU on October 31. I am not aiming for a no-deal outcome,” Johnson, the 54-year-old former Foreign Minister and   erstwhile London Mayor said.

Johnson, whose unconventional style has helped him shrug off a series of scandals in the past has won over much of his party by arguing that only he can rescue the Conservatives by delivering Brexit.