The SDLP has firmly rebuffed a Sinn Fein offer of an electoral pact for next year's Westminster election.
In a dramatic overture on the eve of the SDLP's annual conference, Martin McGuinness urged his nationalist rivals to pull out of the races in North Belfast, Upper Bann and Fermanagh and South Tyrone.
However, rather than a nationalist front, he characterised the move as an effort to maximise the number of parliamentary seats for "pro-Agreement" parties.
Any deal could cost his power-sharing partners the DUP their deputy leader Nigel Dodds' seat in North Belfast and the Upper Bann seat the DUP's David Simpson won from David Trimble, while securing Michelle Gildernew's Sinn Fein seat in Fermanagh and South Tyrone, where she held on last time by a handful of votes.
In return, the Deputy First Minister said his party would stay out of other constituencies - perhaps South Belfast, which would give SDLP leader Alasdair McDonnell a clear run.
Mr McGuinness said the SDLP risked handing the trio of seats "to anti-Agreement unionists", which would be a setback for the political process and encourage the Government's shift towards supporting "negative unionism".
"In response, Sinn Fein is prepared to withdraw candidates in other constituencies to reciprocate," the former Mid Ulster MP added.
Former SDLP Executive minister Alex Attwood, however, hit back. He said: "Our question to Martin McGuinness is; northern nationalism and Irish democracy has never followed the lead of unionism. Why now should we follow what Peter Robinson (DUP) and Mike Nesbitt (UUP) are trying to do in reducing elections to a head count?
"Irish nationalism and Irish democracy is bigger and better than what unionism reduces politics to." But any pact on the unionist side could lead the SDLP to reconsider.
Mr Dodds appeared to indicate yesterday that behind-the-scenes discussions were under way.
"The discussions and details are best worked out away from the glare of publicity," he said.
But Alliance chief whip Stewart Dickson warned: "These tribal pacts are anti-democratic.
"It is not up to Sinn Fein or the SDLP to decide who will be the MP for certain constituencies. The public are not fooled by these shabby little backroom deals.
"If the SDLP do step aside in these constituencies, then voters should be aware that they will be left voiceless in Westminster by Sinn Fein."
UUP leader Mike Nesbitt suggested last month his party would stay out of North Belfast in return for a clear run in Fermanagh and South Tyrone, where the UUP polled well in May this year. But Peter Robinson has indicated he would prefer a joint unionist candidate in Fermanagh, where a similar deal in 2010 saw Rodney Connor lose by just four votes.