At the European Parliament’s behest, and over the objections of U.K. Prime Minister David Cameron, the European Union’s governments have proposed Jean-Claude Juncker — a candidate national leaders don’t much admire, who stands for the kind of EU that a growing number of citizens don’t want — as the next head of the European Commission.

The parliament has scored a notable victory — one that it may come to regret.

When it votes later this month to elect its own nominee, the parliament will be putting a “federalist” — meaning a supporter of more powerful EU bodies — in charge of the EU’s already strong executive branch. In addition, it will affirm an interpretation of the EU’s constitution that increases its own weight in the EU’s system of government.

In a previous column, I said the parliament seemed likely to get its way on Juncker even though the EU’s treaties gave it only an advisory role. This was incorrect, as one reader pointed out. Under the current rules, national governments propose a candidate, taking elections to the EU parliament into account. The parliament then votes, and if the nominee fails to get majority support, governments must put forward another. Under the treaty, the parliament not only advises, but it also has a veto.

This arrangement can be understood in two ways. According to one view, national governments nominate and the parliament decides whether to confirm — much as a U.S. president nominates top officials and the Senate says yes or no. According to the other view, national governments are essentially bystanders. The parliament chooses, and governments facilitate.

One rule, two vastly different interpretations. The parliament asserted the second when it told governments whom to present for its approval, and the governments have just endorsed that understanding. The head of the commission is no longer a bureaucrat chosen by consensus of elected national leaders. Henceforth the job is expressly political, and incumbents will claim a democratic mandate — one that most of Europe’s voters didn’t know they were granting.

Perhaps you’re wondering, how can a mandate that voters don’t know they’re granting be a mandate? That kind of question comes up a lot in the EU.

The Financial Times rightly calls it “a historic shift of power.” It’s a big step from a Europe of nation-states to a European state. Why then might the winner come to regret it? Because it’s such a compelling instance of the pathology that could split the union apart.

The EU’s constitution is in constant motion. Periodically, governments formally recast the rules in ways they don’t fully understand. In between those treaty revisions, the rules are pulled this way and that by EU institutions intent on advancing their own power. Governments, for the most part, look on cluelessly.

The serial failures of this style of innovation — which include the calamitous euro currency system — seem to make no difference. Voters count for nothing either. Support for anti-EU parties reached new highs in the recent parliamentary elections. The coalition of center-right parties sponsoring Juncker has the biggest block of seats in the new assembly, but won only a quarter of votes cast (on a turnout of 43 percent). Those applauding the parliament’s coup call this a triumph for popular democracy.

Next there’ll be an attempt at conciliation. Cameron has said he’ll work with Juncker. (He won’t have much choice.) Juncker will probably be magnanimous in victory, paying his respects to British reservations about further political integration. Other EU governments will move to soften Cameron’s defeat.

Few actually want to see Britain quit the union. Yet the logic of Britain’s exit is looking ever harder to resist.

The EU is institutionally dedicated to the idea of ever closer union, regardless of what its citizens actually want. For too long, the U.K. has deluded itself that this can change. Even now, Cameron is trying to make the case that it can, and that the U.K. can direct the operation. Enough, already.

The alternative to ever-closer union or Britain’s full-frontal exit is to negotiate a new semi-detached status.

Fortunately for the U.K., it has already anticipated this course by standing aside from the ill-fated euro project. Rather than trying to persuade the EU as a whole to change course, Cameron should concentrate now on developing a more comprehensively conceived associate status. That would be better for both the U.K. and the EU than outright divorce — though Cameron may have to threaten a complete separation, and be willing to do it, to get the rest of the EU to go along.

That will be quite a gamble. The U.K. could undoubtedly prosper as a close associate of the EU — as a partner in an enhanced free-trade area — but would pay a crippling price if it left the union in anger and suffered retaliation on trade policy and other issues of mutual interest. If the U.K. government is unwilling to face that risk, the defeat it suffered in the past few days certainly won’t be the last.

For years, Britons who supported the European project argued that the country’s interests would be best served by engaging fully with the EU in order to guide and improve it. That was both arrogant and naive — arrogant because it assumed that the U.K. was entitled to wield disproportionate power, naive because it assumed the rest of the EU would let it. That delusion should now be abandoned.

This doesn’t mean embracing the equally delusional idea that Britain can afford to be on unfriendly terms with the rest of the EU: The costs of an angry split, if it comes to that, would be enormous. Still less should it mean adopting the chauvinism and xenophobia of the anti-EU populists. But the gap between what the U.K. wants and where the EU is headed is just too wide. And it’s time, finally, to admit that it won’t ever close.

Clive Crook is a Bloomberg View columnist and a member of the Bloomberg View editorial board.