The UK’s governing Conservative Party have had their parliamentary majority reduced to just one seat after losing at a special election to the anti-Brexit Liberal Democrats, supported by two other small parties who did not run candidates to give them a better chance of success.

In the Conservatives’ first electoral test since Johnson became prime minister nine days ago, the party was defeated for the seat of Brecon and Radnorshire in Wales by Jane Dodds of the opposition Liberal Democrats. Dodds won 43% of the vote, while Conservative Chris Davies, who was fighting to retain the seat after being convicted and fined for expenses fraud, got 39%.

The defeat reduces the headroom for the government to deliver Brexit as promised by the end of October to nothing, making the chances of both a snap general election and a Brexit betrayal fractionally greater today. The governing Conservatives are already a minority party in Parliament, being supported by small regional party the Democratic Unionists, who want to see Brexit delivered and the United Kingdom held together against the forces of regional nationalism.

In her victory speech, Dodds urged the prime minister to “stop playing with the future of our communities and rule out a no-deal Brexit now.'”

She said “a no-deal Brexit would be a disaster for our farming and agricultural communities.” The constituency she now represents is a hilly, largely rural area about 175 miles (280 kilometers) west of London.

In Britain’s 2016 referendum, the constituency voted by 52%-48% to leave the EU, which exactly matched the national result. While many farmers back Brexit out of frustration with the EU’s rules-heavy Common Agricultural Policy, sheep farmers in Brecon worry that, without an EU divorce deal, steep tariffs on lamb exports will devastate their business.

The result reflects the seismic effect the U.K.’s decision three years ago to leave the 28-nation EU has had on the country’s politics, with voters increasingly split into pro-Brexit and pro-EU camps. The pro-EU Liberal Democrats have seen their support surge because of their call for the U.K. to remain in the bloc. In European Parliament elections in May, the party took 20% of U.K. votes, trouncing both the Conservatives and the main opposition Labour Party, whose leadership is divided over Brexit.

The Conservatives, meanwhile, are losing support to the Brexit Party led by longtime euroskeptic figurehead Nigel Farage, which took 10% of the votes in Brecon.

For the Brecon by-election, the Lib Dems made a pact with two other pro-EU parties, which did not run to give Dodds a better chance. The country’s main opposition Labour Party, whose leadership is divided over Brexit, saw voters desert it and won just 5% of the votes.

The Conservatives lack an overall majority in the House of Commons, and rely on an alliance with 10 lawmakers from Northern Ireland’s Democratic Unionist Party. The loss of the Brecon seat leaves the governing alliance with 320 of the 639 voting lawmakers – the bare minimum needed to carry votes.

That means Johnson’s government may struggle to pass any legislation and is vulnerable to an opposition no-confidence vote that could trigger an early general election.

The Associated Press contributed to this report