LONDON — Britain’s voters go to the polls Thursday faced with a stark choice between Boris Johnson’s Conservative Party, which is campaigning on a message to get Brexit done, or Jeremy Corbyn’s hard-line left Labour Party. Johnson has what could be a decisive lead in the opinion polls, but tactical voting and the country’s first-past-the-post electoral system, which gives the win to the candidate who gains a plurality of the vote, means there could be surprises when votes are tallied.

Polls close at 10 p.m. local time (5 p.m. ET). The first indication of who will form the next government comes at the same time, with the publication of an exit poll commissioned by broadcasters.