Chris Davies has been forced to stand down as MP for Brecon and Radnorshire in Wales after 10,005 people signed a petition to remove him.
A by-election will now have to be held and it is set to be the first electoral test of the new Conservative leader - Boris Johnson or Jeremy Hunt - as it is likely to happen after 22 July, when one of them takes over from Theresa May as Prime Minister.
Brecon and Radnorshire, an affluent corner of rural Wales, was a safe Conservative seat at the 2017 general election but in this year’s European election Nigel Farage’s Brexit Party topped the poll in Powys - the county in which it is - with 35 per cent, with the Liberal Democrats second on 23 percent and the Tories way back on nine percent.
So the by-election could well be a battle between the Brexit Party and the Lib Dems, who held the seat as recently as 2015.
The Lib Dems held the seat between 1992 and 2015 and will be throwing everything at it in an attempt to win it off the Tories.
They too are engaged in a leadership contest and Lib Dem party members are set to choose between Ed Davey, a former Energy Secretary during the coalition government, and Jo Swinson on 23 July.
The Lib Dem candidate will be Jane Dodds, who said: "Thousands of residents across Brecon and Radnorshire have taken the chance to demand better than a Westminster politics that fails to take their concerns seriously."
The Conservatives will have to pick a new candidate for the by-election as the petition means Mr Davies - who made an "unreserved apology" after he was convicted - cannot stand again.
Mr Davies was fined £1,500 and ordered to do 50 hours of community service.
Earlier this year the Labour MP for Peterborough, Fiona Onasanya, was also forced to step down after a similar petition following her conviction for perverting the course of justice. Despite a strong challenge from the Brexit Party, Labour managed to hold onto Peterborough.