The share of the vote in Brecon & Radnorshire at the 2017 general election was Conservatives 49%, Liberal Democrats 29%, Labour 18%, Plaid Cymru 3% and Ukip 1%.
The Liberal Democrats held the constituency from 1997 to 2015. They would need a swing of 9.8% to retake the seat.
A Lib Dem victory could rejig the parliamentary arithmetic, making it harder for the new Prime Minister to get his Brexit plans through the Commons.
There are currently 320 MPs who – on paper – would back the Government in a crunch vote in the House of Commons – 310 Tories and 10 members of the DUP.
The DUP agreed to support the Conservatives in certain key votes, such as confidence motions and Budgets, as part of a deal reached in the aftermath of the 2017 general election.
The seat of Brecon and Radnorshire is currently vacant, so whoever wins the by-election will increase by one either the Government’s tally of MPs or those of the opposition.
If the Lib Dems win the seat, and, were they to do so, the opposition tally would increase from 318 to 319.
