Anthony Steen announced in May he would stand down at the election
Ballot papers are being sent to all 69,000 voters in Totnes to help choose a replacement Tory candidate to contest the seat in the next general election.
The Devon MP Anthony Steen said he would stand down at the next election after reports of his expenses were made public by the Daily Telegraph.
The Conservative Party says it will be the first "open primary" contest held by a British political party.
Totnes Conservative Association has shortlisted three potential candidates.
Candidates are normally selected by their local party.
The contenders are Nick Bye, Sara Randall Johnson and Dr Sarah Wollaston.
Mr Bye is Torbay's mayor, Ms Randall Johnson leads East Devon District Council and Dr Wollaston is a GP.
The candidates are to set out their stalls and allow people to ask questions during an event on Saturday at Torbay Leisure Centre, starting at 1030 BST.
The results will be announced on 30 July.