The Union has to change too

A larger Union is a different Union. That is not an argument against enlargement; it is a statement of arithmetic, and the member states have been discussing it openly.

The questions enlargement forces

Voting. Unanimity in areas such as foreign policy and taxation becomes harder to reach with each additional member, and the practical consequence is either paralysis or an extension of qualified majority voting into new areas. That is a genuine transfer of sovereignty and member states are entitled to weigh it carefully.

Budget. Cohesion and agricultural spending are allocated by formulas that a new large member would change substantially. Every existing net recipient has an interest in how that is handled.

Institutions. Commission size, parliamentary seats and the rotating presidency all scale awkwardly.

The sequencing argument

One view holds that internal reform must come first, or the Union will be unable to function after enlarging. Another holds that making reform a precondition gives any member an indefinite veto over enlargement.

Both positions are held sincerely and neither is a bad-faith argument.

What the record suggests

Previous enlargements were accompanied by treaty adjustment rather than preceded by completed reform, and the adjustments were made when the accession made them unavoidable.

Why a candidate should follow this closely

Because the terms of accession will be shaped by these debates, and a candidate that understands the internal arithmetic negotiates better than one that treats it as somebody else's business.

That enlargement opens questions on the other side too is familiar from partnership negotiations: when a new partner comes in, the existing ones recalculate their shares, and that is not the newcomer's fault. A candidate should follow it closely because its own timetable depends on that internal argument — which it cannot accelerate; it can only keep its own side ready.