Brexit. Brexit. Brexit. And Boris Johnson. That’s what’s on as Britain’s Conservative Party meets this week at Manchester, England. Poor Theresa May, prime minister and leader of the rancorous Tories. She is persona non grata for many delegates, although most are too polite to say so. Once enjoying the respect, if not the love, of the party whose lead she assumed when David Cameron resigned office to let others oversee the United Kingdom leave the European Union, Mrs. May is now reviled as the leader who called an unnecessary election that was hers to win and then to lose.

Which left her humbled before Parliament to manage a minority government propped up with discordant Irish unionist support. The embattled Prime Minister is routinely dissed as the one-time “Remainer” who seems set to bottle Brexit. Into this leadership maelstrom swirls the Foreign and Commonwealth secretary, Mr. Johnson.

A Telegraph article in mid-September was Boris Johnson’s first salvo over No. 10’s transom, in which he lays out his “glorious Brexit blueprint.” He conjures up all manner of exploits, from regulatory and tax reform to technical and financial innovation, where Britain will triumph again. And he drives home the case for Brexit, as the patriotic response to an evolving Euro-federalism — “an attempt not just at economic but political integration of a kind that the British people had never bargained for” — that was the impetus for the “Independence Day” referendum results of June 2016. “That plan is simply not for Britain,” Mr. Johnson writes, “and we should have been more honest about it years ago.”

Given a troubling dirigisme in Mrs. May’s domestic policies, Mr. Johnson’s few asides toward a libertarian agenda are encouraging, if politically unrealizable. On political economy, he lauds the 19th century French economist Frédéric Bastiat whose “unseen opportunity cost” refutes “the way the UK economic structure has evolved to fit the EU over the last four and a half decades.”

Meanwhile, a week-end interview with London’s Sun ratchets up Tory tensions, contrasting Mrs. May’s flaccid Florence speech (criticized for covert compliance with EU demands) with a resolute Mr. Johnson, “establishing himself as the defender of the true Brexit faith.” His four “red lines” entail complete negation of EU influence over the UK: “No,” to shadowing Brussels’ regulations to encourage continuing relations; “no” to European Court of Justice oversight; “no” to paying for single market access; and “no” to “transitioning” beyond two years. “There is no point in coming out of the EU and then remaining in rotational orbit around it,” Mr. Johnson insists. “That is the worst of both worlds. You have to be able to have control of your regulatory framework.”

Is Brexit revitalized under Boris Johnson? Your cynical Brexit diarist eschews such enthusiasm. As I have cautioned before, far better for Theresa May to remain leader and allow a focussed Government to negotiate Brexit, in the best Westminster tradition of Cabinet solidarity. For better or worse, any bad press accrues to her as Prime Minister, leaving an eventual replacement to assume office with a clean slate — and none of her putative heirs-apparent are without political baggage. Already there is a “Stop Boris” movement among Tory MPs, signalling that Conservative infighting is not exclusive to the faltering May ministry. Excepting Mr. Johnson’s current moment in the limelight, there are no ready successors to Mrs. May — save, horror of horrors, Labour opposition leader Jeremy Corbyn.

It is, though, undeniable that Boris Johnson’s élan is sorely needed as Britain is perceived to be at the mercy of wily European counter-negotiators. Brexit jubilation has dissipated as the clock ticks toward March 2019 and the prospect that Britain will be hoodwinked: still subject to the European Union and sovereign in name alone. So when Mr. Johnson assures his British readers that Brexit “is going to be great” and “we need to believe in ourselves and believe we can do it,” he strikes a responsive chord. Mr. Johnson’s “ain’t no stopping us now” is just what Brexiteers need to hear.