In order to fully appreciate the impact of Brexit on the composition and political dynamics of the European Parliament, it might just be best to consider what it would look like if Brexit weren’t happening at all.

Whilst this remains rather unlikely, two scenarios could see the UK participate in the European Parliament elections on 23-26 May 2019. The UK could still revoke Article 50, thereby remaining a Member State for the foreseeable future and halting the Brexit process, but more likely a long extension to the Brexit negotiating period could be agreed which would legally require the UK’s participation.

So let’s consider what would happen under these scenarios.

The reallocation of the UK’s 73 seats in the European Parliament, as agreed back in June 2018, would not come into effect. In the extension scenario, the reallocation would eventually come into effect following the UK’s departure.

What this would mean in concrete terms is difficult to predict, as the composition of a UK delegation cannot be taken for granted and would be dependent on the outcome of the election in the UK.

In addition, and quite understandably, polling has not been conducted on UK voter sentiment ahead of an election that simply wasn’t supposed to take place.

The European Parliament’s own polling reports use national voting intentions as a proxy for European election voting intentions where such data is unavailable. Utilising this approach for the UK, a rough average of polling from 15 March 2019 finds the Conservatives and Labour both sitting in the mid-30%s. If they polled similarly in an election in May, they would improve on their respective shares in the 2014 European election, 23.1% and 24.4% respectively, which translated into 19 and 20 seats.

Of course, in that election, the United Kingdom Independence Party (UKIP) polled 26.6% taking 24 seats. However, since the Brexit referendum, UKIP’s existence as a cohesive political force in British politics has waned. On this basis, we can make an assumption that the Conservatives and the Labour Party would increase their shares of the vote which, under proportional representation, would necessarily translate into more European Parliament seats.

It’s here that we start to really see the impact of the UK’s participation in the elections and any UK delegation taking up its seats. Most strikingly, at first glance the European Conservatives and Reformists (ECR) would retain a Conservative delegation, thereby adding an extra 24 or so to its seat share.

Commentary on the future of the ECR post-Brexit has drawn the conclusion that it would likely be unsustainable as a political group in the 2019-2024 Parliament due to the loss of the UK Conservative delegation. The continued viability of the ECR could act as a stumbling block to the formation of a more cohesive right-wing grouping.

However, perhaps the more fundamental impact would be on the waning fortunes of the Socialists & Democrats (S&D). The S&D are projected to lose around 60 seats, a third of which is due to the loss of the 19 strong Labour delegation. Factoring in the inclusion of a Labour delegation would see the S&D lose “only” around 40 seats. Under this scenario a degree of unexpected stability would be given to the grand coalition between the centre-right EPP and the centre-left S&D that has for so long dominated European Parliamentary politics.

Of course if the UK were to revoke Article 50, this situation would be greeted with a significant degree of warmth in a Brussels bubble fearing the impact of a realignment of the political balance in the EP away from the centre, with the introduction of MEPs with a more nationalistic bent. Those in the bubble would be able to breathe a sigh of relative relief.

However, should the UK participate in the elections and remain a Member State for an extended period into the new mandate, the presence of the temporary UK MEPs would pose important questions for the ability of the European Parliament to function legitimately. With an additional 20 or so MEPs, the S&D would be in a position to demand a greater share of the spoils in terms of Committee responsibilities, speaking time, and roles on important legislative files.

This influence early on in the legislature would have ripple effects through to the end of the mandate in 2024. As it stands, a solution hasn’t yet been proposed to how this influence would be unraveled, should the UK ever finally leave the EU. With the possibility of a long extension still on the table pending events in the UK, solutions to thorny political and legal problems would need to be found fairly hastily.