Boris Johnson, the mop-headed face of Brexit, emerged last week as an early frontrunner to succeed Theresa May as British prime minister after she announced she would step down in early June. (“I negotiated the terms of our exit and a new relationship with our closest neighbors that protects jobs, our security, and our union,” she lamented. “I have done everything I can to convince MPs to back that deal. Sadly, I have not been able to do so.”) But his heir-apparent status may already be in question. On Wednesday, a London judge ordered Johnson to appear in court over allegations that he misled the public during the 2016 campaign for the U.K. to leave the European Union. According to a summons by private prosecutor Marcus Ball, Johnson—a member of Parliament and former London mayor—“repeatedly lied and misled the British public as to the cost of E.U. membership,” falsely claiming that the country was paying Brussels 350 million pounds per week.

Johnson has dismissed the allegation as a politically-motivated stunt, but District Judge Margot Coleman ruled Wednesday that the case warranted a preliminary trial at the very least. “The allegations which have been made are unproven accusations and I do not make any findings of fact,” Coleman said. But, “having considered all the relevant factors I am satisfied that this is a proper case to issue the summons as requested for the three offenses as drafted.”

The stunning ruling will compel Johnson to answer charges that he purposely misled the public about the costs of Britain’s alliance with the E.U. to swing the Brexit vote in his favor. So far, however, it’s unclear how the matter will impact the race to replace May in Tory leadership. While misleading the public may not be a big deal here in the United States — where Donald Trump exaggerates, obfuscates, bamboozles and flat-out lies multiple times per day — the misconduct offenses Johnson is accused of could carry a maximum sentence of life in prison, according to the Guardian. (The London-based fact-checker, FullFact, notes that E.U. membership is considerably lower than 350 million pounds per week with rebates.)

Of course, there are several steps between a court summons and imprisonment. Johnson will first appear at an administrative hearing, which will be followed by a preliminary crown court hearing where the hardline Brexiteer will likely seek to have the case thrown out. If the case gets to a full jury trial, it likely wouldn’t be for several months—at point which Johnson may already be prime minister. The summons will likely rally supporters around him, but it could also reinforce Johnson’s image as a political liability, potentially wounding his shot at Britain’s highest government office. His political opponents have already seized on the ruling, arguing that it disqualifies both Johnson and his party from leadership. “The Conservative Party are not fit to run this country,” Liberal Democrat MP Wera Hobhouse tweeted Wednesday.

Nor is it totally clear how the case would impact Brexit negotiations, even if the referendum was passed in part thanks to Johnson’s lie. Ball has said that the purpose of his campaign isn’t to disrupt Brexit, though it could keep the face of the British leave, who’s spoken favorably of a “no deal” withdrawal, from leading the country. At least two Tory challengers, Jeremy Hunt and Matt Hancock, have warned against the cliffs’ edge Brexit endorsed by Johnson. But close competitors like Dominic Raab, the former Brexit secretary, also favor a no-deal leave if MPs fail to strike an accord, suggesting that the U.K.’s nightmare scenario may play out whether Johnson finds himself at 10 Downing Street or in the slammer.

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