Change UK launched its European Parliament election campaign Tuesday. Assuming the ballot goes ahead in the country, it will be the party's first electoral test since 11 Tory and Labour MPs left their respective parties to form The Independent Group on the opposition benches in parliament.

The event follows the campaign launch of Nigel Farage's Brexit Party earlier this month — with an immediate impact in the polls. One YouGov poll put the Brexit Party at 27 percent, while another conducted by ComRes around the same dates had the party on 17 percent.

Impressive for a brand new party, but we should take the numbers with a pinch of salt. The differences between the two polls cannot be explained by methodological differences in the polling alone, and they point to the high uncertainty we face when it comes to measuring the voting intentions of U.K. electors in a contest for MEPs who may hold their seats for just a few months.

POLITICO's Poll of Polls aggregates the results from multiple opinion polls (in the U.K. and across the other 27 EU countries) to give a more consistent indication of party support. Our analysis puts Farage's party on 19 percent, behind Labour on 26 percent and just ahead of the Tories on 17 percent. Labour's current position is about 1 percentage point higher than the result it achieved in the 2014 European election, while the Tories are about 6 percentage points lower.

The Brexit Party looks to be capitalizing on the collapse in support for UKIP, which won the last European election with nearly 27 percent, but is now down to 7 percent.

As for the parties backing a second Brexit referendum: Change UK is at 7 percent; the Lib Dems are on 9 percent; the Greens on 8 percent; and the Scottish National Party on 4 percent. If Remainers view Labour's campaign stance on Brexit as not definitive enough though, any or all of these parties could benefit significantly.

Whatever the result, the U.K.'s participation in the election — again, assuming it happens, which at present Prime Minister Theresa May says she is working to avoid — will have a significant impact on the makeup of the European Parliament.

In preparation for Brexit, the EU27 reallocated 27 of the 73 U.K. seats among the other member countries and reduced the total number of seats in the Parliament from 751 to 705. With the U.K. back on board, countries that had expected to benefit from the rebalancing, such as France and Spain, will not receive those extra seats.

We can use POLITICO's daily updated seat calculation, based on polls across the EU, to project what difference the U.K. participation will make. Without the U.K. in the mix, the seat projection is relatively stable. The right-of-center European People's Party is well ahead with around 178 seats and a lead of about 45 seats over the Socialists and Democrats (S&D) group. The Alliance of Liberals and Democrats for Europe (ALDE), combined with Emmanuel Macron's En Marche, look likely to pick up close to 100 seats. The European Conservatives and Reformists (ECR), currently home to the U.K.'s Tories, can expect around 53 MEPs.

If the U.K. does take part, then Labour and the Tories would, according to the current aggregated polling, pick up 20 and 12 seats respectively, with those seats most likely going to S&D and ECR. Change UK and the Brexit Party have not yet said which political grouping they would join.

That boost to the S&D is slightly blunted by the indirect impact of the U.K.'s participation though — in the form of those reallocated U.K. seats. With the U.K. on board, Frans Timmermans' S&D group has a net gain of 14 seats compared to the U.K. not taking part. That's because the reallocation would give them extra seats in other countries, according to the projection.

So having the U.K. in the mix puts the S&D closer to the EPP, but even then it looks like they will fall well short of dislodging the center-right group from the top slot.