It’s official: the United Kingdom will have elections to the European Parliament, almost three years after the UK voted to leave the European Union and the best part of two months after the UK was supposed to leave under the Article 50 process – assuming, that is, that the 27 other member states of the EU accept the British government’s request for an extension.

Whatever happens, these elections are now set to be among the most consequential in British political history, whether the United Kingdom ends up contesting them or not.

Theresa May’s hope is that the prospect of holding European elections will finally scare up a parliamentary majority for her withdrawal agreement. That prospect is, however, slim: that she has already opened up talks with the Labour leader, Jeremy Corbyn, increases the political cost to Labour MPs of breaking ranks to back her accord in its current state. May is at or near the maximum level of support her deal can attract from Conservatives and she may even lose ground among Tory MPs next time the withdrawal agreement is voted on.

The bigger political event will be when these elections really begin to come into view. Pro-Brexit MPs, whether they voted to leave or to remain, have long feared that holding European elections would provoke a political backlash. One MP in a marginal constituency recently told me that their constituents would “burn my office to the ground” when they received their polling cards in the mail.

If the European elections are the cause of a political earthquake, whether because the fact of holding them triggers a political storm or because the contests produce two victories for pro-Brexit forces, then that will strengthen the hand of MPs urging a quick deal to take the United Kingdom out of the EU.

If the EU elections are a political non-event or they result in victories for pro-European politicians and parties however, then that will have the opposite effect, boosting the cause of those who want the softest possible Brexit, or no Brexit at all.