Did EU citizens decide the outcome of the 2019 Hungarian local elections?

As reported by index.hu, Fidesz politician Lajos Kósa claims the Budapest mayoral elections were decided by the 90,000 EU citizens who are eligible to vote in the capital. However, is his claim valid?

According to the electoral data, only 38,021 EU citizens were eligible to vote in the Budapest mayoral elections; this is less than 50% than the figure claimed by Kósa .Since there are 1,446,458 registered voters in the capital overall, they only make up 2.6% of this number.

Gergely Karácsony defeated Fidesz candidate István Tarlós by 46,000 votes, meaning that if we assume that every single EU citizen voted for Karácsony, and then we subsequently take away these votes, Karácsony would still have come away victorious. The turnout for the election was 45.58% overall, making it very unlikely that all EU citizens voted anyway.

However, when we consider election results on the district level, the story is quite different. In 10 out of Budapest’s 23 districts, candidates won by a margin which is less than the number of EU citizens living in the area. Four of these districts were won by Fidesz or an ally of Fidesz (Districts V,  XII, XXIII and XX) and six were won by the opposition (Districts I, II, III, VI, VII and VIII).