LONDON — There was an odd feeling in the air Thursday, almost one of suspended animation, as Britons voted in elections for a European Parliament that Britain was supposed to have quit by now and lawmakers took a day off from their back-room machinations to oust Prime Minister Theresa May.

At polling stations around the country, people lined up to take a thwack at the main parties, Conservative and Labour, with Leavers streaming to a Brexit Party that did not exist four months ago and Remainers to the Liberal Democrats, previously seen wandering in the political wilderness.

Outside polling stations on the eastern edge of London, among the very few parts of the capital that voted for Brexit in 2016, people poured out their frustrations, fed up with the ineptitude, indecision and chicanery that they said had knotted up British politics for three years.

Jane Sykes, a supporter of Nigel Farage’s upstart, single-issue Brexit Party, said simply: “The main parties have lost it.”