Boris Johnson, the front-runner to succeed Theresa May as U.K. prime minister, pledged a hard line on Brexit — including the option of leaving without a deal — as contenders to lead the Conservative Party sought support before the list of candidates is finalized Monday.

Johnson, who also said he would scrap the Irish border backstop and withhold £39 billion ($50 billion) owed to the European Union until an agreement is reached, was helped by the discomfort of Environment Secretary Michael Gove, who saw his campaign submerged under revelations that he used cocaine decades ago.

"Yes, it was a crime, it was a mistake, I deeply regret it," Gove told the BBC as he tried to switch attention away from his past drug use toward his plans to cut sales taxes and renegotiate a deal with the EU. As justice secretary, "one of the things I said was that people should never be defined by the worst decision that they make, but should be given a chance to redeem themselves and to change," Gove said.