Brexit Triumphant or Brexit Bust? With little more than two weeks before the March 29 deadline, many factors are still in flux. Pending votes in Parliament this week will give direction to the final outcome. Prime Minister May’s “Strasbourg stitch-up” only distracts from a deal that cedes too much to the European Union while continuing to frustrate full British independence.

Mrs. May joined EU officials late Monday for eleventh-hour negotiations to save her withdrawal agreement. She emerged little over an hour later with European Commission president Jean-Claude Juncker, to announce “legally binding” changes that putatively take the sting out of the Irish backstop.

“Now is the time to come together, to back this improved Brexit deal, and to deliver on the instruction of the British people,” she said.

Succeed or fail, Mrs. May will bring her “improved” exit proposal to Parliament on Tuesday for another vote. Her first attempt in January, it will be remembered, failed by an astonishing 230-vote margin. MPs feared the Irish backstop left the UK under EU customs oversight, minus a legal mechanism to get out.

If history repeats itself and the agreement goes down to defeat again, on Wednesday the House of Commons will test its will on a “no deal” Brexit.

If this too fails, Thursday’s vote will ask Parliament to petition the EU for an extension of Article 50. If successful, and Brussels accedes — under doubtless punishing terms — the dreams of Brexit will be fairly vanquished.

Contemplating these dire circumstances under its own lights, the London Spectator came out in favor of the withdrawal agreement. If the Attorney-General is able to resolve the Irish backstop impasse, it advises “Brexiteers, whatever their wider misgivings, should hold their noses and vote for Theresa May’s deal.”

Following Mrs. May’s Strasbourg intervention, the UK Sun agrees that Tory MPs must “back this deal.” Acknowledging that the Prime Minister’s “Brexit deal is not as good as the Government claims, nor quite as bad as its detractors believe,” continuing the fight has diminishing returns. Among them, a second referendum or possibly a general election, the tabloid warns.

“There is no task more important to the warring Tory Party than keeping Corbyn’s Marxists out of power,” the London Sun editorializes. “No, not even Brexit.”

I beg to differ. “Brexit longa, Labor brevis,” to mangle a famous adage.

True, disregarding Labor’s socialist aspirations is foolhardy. State takeover of essential services such as energy and transportation; punitive employment and regulatory measures that enervate free enterprise; plus a return to tax-and-spend policies that suffocate Britain’s entrepreneurial growth — all highlight Labor’s anti-capitalist agenda.

Moreover, were Jeremy Corbyn to come to power while Brexit negotiations are ongoing, Brexiteers’ worst fears could become reality. Humiliating exit terms with the EU. That dreaded second referendum. Even, possibly, abandoning Brexit itself.

Such fear-mongering, however, fails to take into account that the Labor party’s own house is in disorder. The Independent Group, while counting a few renegade Tory MPs among its number, is composed principally of disaffected former Laborites. They bolted on claims their party is adopting far-left policies — and with anti-Semitic undertones. The Group’s main source for recruits lies on Labor, not Conservative, backbenches.

The worst blow to British political stability, though, is not the specter of a Labor government, although Mr. Corbyn has, in his brief term as leader of the opposition, left Britons in no doubt of how Labor would participate in the march by the EU toward an administrative super-state.

No, the unkindest cut would be to betray Brexit.

To support a flawed withdrawal agreement on questionable guarantees, on the assurance of an EU bureaucracy infamous for interpreting any agreement in its self-interests — member countries be damned — when the benefits of “WTO Brexit” is within your grasp, is an unconscionable betrayal of British independence.

That betrays the British people and their unambiguous 2016 referendum decision to “Leave the European Union.” As Tory MPs contemplate the fate of Brexit, they must realize they would share the fate of Labor colleagues if they deny the will of the British majority to reclaim their sovereignty.

Otherwise, there is only one response available to British patriots. “A plague on both your houses.” The choice, then, for Tory and Labour alike, should be clear: Vote down Mrs. May poisoned withdrawal agreement. And vote up WTO Brexit and British freedom.

Mr. MacLean, who maintains the weblog The Organic Tory, writes a Brexit diary for The New York Sun.