Alliance leader David Ford today told Sinn Fein "bring it on" as Mitchel McLaughlin dramatically switched to fight for an Assembly seat in South Antrim.
Mr McLaughlin is expected to build on former candidate Martin Meehan's performance in 2003 when he came close to taking Mr Ford's seat.
But the unexpected transfer of the Sinn Fein general secretary from Foyle could also come at the expense of the SDLP.
Mr Ford said today: "Last time Sinn Fein sent in a carpetbagger candidate from north Belfast. They said he would win: at one point they said he had won.
"I will treat the transfer of Mitchel McLaughlin into the area in exactly the same way."
Mr McLaughlin, who had put his name forward for a selection convention in Toome, believes Sinn Fein can gain their first seat in the constituency - but it is a gamble.
"Sinn Fein is determined to continue to build political strength for the nationalist people as a means of ensuring that politics here will continue to progress across this island," he said.
"That means that no constituency will go unrepresented by default.
"Having discussed the situation with family and colleagues - locally and nationally - I believe that securing the South Antrim seat for Sinn Fein is how I can best serve that strategy at this time."
The SDLP is running two candidates in the constituency, Thomas Burns and Noreen McClelland, the wife of former MLA and deputy Assembly speaker Donovan McClelland.
Mr Burns said the party was targeting two seats, having built up a sound support base and strengthened the party organisation across the constituency.