Sinn Féin Senator Trevor Ó Clochartaigh has resigned from the party.
A party spokesperson confirmed the resignation, saying: "The Sinn Féin selection convention in Galway West/South Mayo is due to be held this weekend.
"Trevor Ó Clochartaigh had been making the case for a two candidate strategy up until yesterday.
"Given the party didn’t make the quota or elect a TD in the last election we were going with a one candidate strategy on this occasion.
The spokesperson also said: "It is clear that Trevor was worried that a democratic vote of party members in the constituency would not select him to contest the election."
Mr Ó Clochartaigh was elected to the Seanad in 2011 and again in 2016 on the agricultural panel.
He was Sinn Féin spokesperson for Irish language and Gaeltacht affairs, rural development and the Diaspora - as well as Seanad spokesperson on housing and local government.
He was also the Sinn Féin candidate in Connemara for the local elections in 2009 and the general elections of 2011 and 2016.
A page with the Senator's biography has been removed from the Sinn Féin website.