The most difficult obstacle to a Labour Party merger with Democratic Left is not the future of State-owned industry or how to target tax cuts. It is Dublin North West.
In this three-seater sit the Democratic Left leader, Proinsias De Rossa, and the formidable Labour deputy, Roisin Shortall. In the last election, Ms Shortall retained her seat at a difficult time for Labour with over 1,000 votes to spare. Mr De Rossa scraped in by just 100 votes.
That was when there were four seats. Now there are three and, barring a swing of truly momentous proportions to a new Labour Party, one must lose.
Dublin North West is the most extreme example of constituencies where rivalries between Labour and Democratic Left deputies and organisations threaten the smooth passage to a merger of the two parties. Some Labour sources, for example, suggest a precondition for the deal will be that De Rossa gets out of the constituency.
Democratic Left sources say De Rossa has held a seat there for six elections, and has contested the constituency since 1977. "You can't say `We'd love to merge with you and by the way you must screw your leader first'," says one source.
In Dublin South Central, Dun Laoghaire, Wicklow and Cork North Central there are similar problems, although they appear less intractable. All are constituencies where a merged party would have to put up two candidates if its stated aim of substantial growth was to be seen as credible. In these circumstances Labour and DL candidates could form uneasy alliances on joint party tickets.
It is a measure of how far advanced the merger process is that deputies and party activists in both parties contacted this week pointed only to the constituency problems.
There is no policy difficulty. A general "mission statement" outlining central principles for a new party has been drawn up. Immediately after the 1992 general election the two parties drew up a detailed joint policy document. Nobody expects any problem in agreeing a policy platform now.
"It is quite clear that people are concerned about their own political futures," says the leader of Labour's negotiating team, Mr Brendan Howlin. "Those concerns will inform our dialogue. But the objective is that the end result will be greater than the sum of its parts, and that it will be a party with a sharp new message that can shape the agenda for the new millennium."
As Labour's deputy leader, Mr Howlin is understood to be under some pressure to make a personal concession for the good of the new party. The idea of a second deputy leader - either Mr De Rossa or Mr Pat Rabbitte - has been floated as part of the deal to accommodate the deputies from the two parties on the one front bench. Individuals on Labour's current front bench will be asked to move over. The idea of the second deputy leader is to reduce the number who will be discommoded.
Both parties say publicly that there is no deadline, but there is in practice. Local government and European Parliament elections take place next June. If the parties are by then still discussing a merger, they have no credibility standing as separate parties in those elections. If they want a single party by then, it will have to happen months before so selection conventions can take place.
Democratic Left has a party conference organised for November. The Labour leader, Mr Ruairi Quinn, has said that a special Labour Party conference could be held to approve a deal shortly after that. The private aim is to have Mr Quinn, Mr Howlin, Mr De Rossa and Mr Rabbitte clasping each others' hands on the platform of a Labour Party conference before Christmas. "It happens by Christmas," says a DL source, "or it doesn't happen at all."
Any new party will be called the Labour Party, will have Labour's existing ruling structures and Labour's current leader. Seats on the party executive will be given to Democratic Left figures as an interim measure. Labour's next biennial conference is in April. It would be a perfect platform from which to launch an election campaign on behalf of the new, united party.
There are those in both parties who question the rush. Ms oisin Shortall of Labour is among them although not, she insists, entirely for reasons of personal political survival.
"The experience in other European countries is that the combined representation of merged parties is often less than was achieved as separate entities," she says. "In the 1992 election there were constituencies where Labour and Democratic Left each won seats through each having our own distinctive appeals." This distinctiveness is an advantage to both, she says, and will be lost in a merged party.
Also the assimilation of Democratic Left would create space on the left for the growth of Sinn Fein and the Socialist Party of Mr Joe Higgins TD to grow into alternative left groupings, she says.
Within Democratic Left, too, there are those who are proud of their party's separate identity. At today's meeting of the executive in Dublin, according to one source, there will be individuals who voted some months ago to open exploratory discussions with Labour about a possible alliance, but will now be horrified that the party might cease to exist within three months.
More and more party members have come round recently to the idea that a merger is inevitable, say DL sources. There will be some ideologically based objections today from people who see it as primarily a political pressure group on behalf of the poor and marginalised rather than one seeking places in government, says one source. But they are expected to be in a minority.
If Democratic Left's executive approves it today, the talks will move into detailed, local discussions in the coming weeks to try to resolve the constituency rivalries. Sources in both parties predict that Dublin North West will be the last to be negotiated. Nobody can think of a solution.
DL sources say there is no question of Mr De Rossa solving the problem by standing for the European Parliament. Labour sources dismiss DL suggestions that Ms Shortall could move to Dublin Central, to which a part of her vote has been moved in the recent constituency boundary revision.
Dublin Central's Labour Senator Joe Costello, though politically close to and personally friendly with Ms Shortall, would also have views on this prospect. The newly created constituency of Dublin Mid West has no obvious Labour/ DL front runner, though it is doubtful if one of the two could be transplanted to the new entity.
By the time they sit down to decide it, however, it may be impossible to put on the brakes. As Labour's finance spokesman, Mr Derek McDowell, says: "If we get that close and then walk away over what the public will see as personality squabbles, we will all look very silly."