LONDON (AP) — New British Prime Minister Boris Johnson is facing his first electoral test — a special election that could see the Conservative government's working majority in Parliament cut to just one vote.

Voters are electing a new lawmaker for the seat of Brecon and Radnorshire in Wales on Thursday after Conservative incumbent Chris Davies, was ousted. He was dumped by a petition of electors after being convicted of expenses fraud.

Davies is running to regain the seat but faces a strong challenge from the Liberal Democrats in a vote overshadowed by Brexit.

Johnson became prime minister last week, vowing to take Britain out of the European Union on Oct. 31, with or without a divorce deal.

The pro-EU Lib Dems are hoping to win support from voters opposed to Brexit.