Normally an outsider trying to negotiate the sectarian geography of Northern Ireland might need the help of a little local knowledge. In election times, however, an alien from another galaxy could quickly work out where Catholic territory ends and Protestant territory begins. Even in the intricate patchwork of North Belfast, simply following the election posters solves the problem with almost mathematical precision.
In the few feet that separate Torrens Avenue from Torrens Crescent, for example, or Rosapenna Street from the Hillview Enterprise Park, the posters for Sinn Fein's Gerry Kelly end and those for the DUP's Nigel Dodds begin. The election posters signify even more than the churches do. The stern bulk of Oldpark Presbyterian Church may suggest that this part of the Cliftonville Road is still unionist. But the even sterner face of Gerry Kelly staring down from the lamp posts either side of it show that Catholic settlement has drifted up from older strongholds.
The Belfast Agreement was supposed to break through this iron triangle of religion, politics and territory. The hope was that new alignments, forged from daily social and economic concerns, would begin to replace the politics of sectarian division. The implementation of the agreement has been so fitful and tortuous, however, that the election is being fought on the old battleground.
The mentality that views an election primarily as a sectarian headcount has not shifted. David Trimble reinforced it when he advised his supporters to transfer in the local elections to pro-Union rather than to proagreement candidates: code for keeping the vote within the tribe.
Nationalist opinion, meanwhile, may not even bother with the codes. In his column in the North Belfast News last week, the Gaelic language activist Gearoid O Caireallain was clear that the main point of the election was to show there are more Catholic than Protestant voters. Thus the internal war between the SDLP and Sinn Fein in the constituency is a good thing, because it would get out the Catholic vote and "bring us one marker closer to that magical 50 per cent plus one".
The Westminster first-past-the-post system reinforces this mentality. Thus, the appeal to voters on each side of the sectarian divide in North Belfast is the same. Neither the nationalist candidates nor the unionist candidates seem to bother arguing the relative merits of nationalism or unionism. The question that matters most is which candidate can stop the other side from taking the seat.
With the veteran Ulster Unionist Cecil Walker seemingly on the way out, the new tribal figurehead on the unionist side is Nigel Dodds. So the SDLP's Alban Maginness is campaigning under the slogan "Only Maginness can beat Dodds". Gerry Kelly's slogan is "It's Kelly or Dodds". Nigel Dodds, meanwhile, is wooing the voters of Tiger's Bay and Rathcoole with the slogan "The Only Unionist Who Can Win".
The notion that keeping them out is more important even than the agreement distorts the whole process. South Belfast, for example, is the most pro-agreement constituency in Northern Ireland. But it will almost certainly re-elect an anti-agreement MP, Martin Smyth, simply because many moderate unionists fear that a vote for the Women's Coalition or the Alliance Party could hand the seat to Sinn Fein or the SDLP. To treat such votes as a rejection of the agreement would simply be wrong.
Likewise, in the psychologically important South Antrim constituency, the likely victory of the DUP's William McCrea could be misleading. The Alliance candidate there, David Ford, says he would have seriously considered pulling out and urging his supporters to vote for the UUP were it not for the fact that the UUP candidate, David Burnside, is at best deeply ambivalent on the agreement.
"Pro-agreement voters," he says, "are simply not motivated by David Burnside. The more people he meets on the canvass, the more people are turned off by him." He predicts a McCrea victory by default.
In this context, arguably the most important and certainly the most emblematic candidate in the election is one who is not standing, the Alliance general secretary, Stephen Farry. He is an experienced and well-regarded local councillor and leader of the Alliance group on North Down Borough Council.
As the place where Alliance was founded in 1970, North Down is the party's heartland. Stephen Farry would probably have taken about 15 per cent of the vote - not enough to take the Westminster seat but enough to make a significant difference to the party's national total.
Yet, in the weird logic of Northern Irish politics, the most constructive thing Stephen Farry could do was to pull out of the election. The largely middle-class Protestant constituency of North Down is heavily pro-agreement but is represented at Westminster by Bob McCartney, leader and sole star of the anti-agreement UK Unionist Party. Even among his own supporters, Farry found that the strongest passion was the negative one of getting McCartney out.
"I would go to the doorsteps and say, `vote Alliance'," he says. "They would say, `Fine. But what's the best way to get rid of Bob McCartney?'. "If I say, `vote Alliance', it's a political deceit." The honest answer, which is the one he decided to give, is to vote for the pro-agreement UUP candidate, Sylvia Hermon.
However honest this may be, it still leaves some Alliance voters feeling disenfranchised. Some, like Bangor woman Karen Banks, refuse to support Hermon, because "I don't want to give my vote to a candidate who is associated with a party which is seriously divided on the Belfast Agreement".
Stephen Farry, who is standing in the local elections, acknowledges a divided reaction among his supporters. "On the doorsteps," he says, "of every 10 people, three will spontaneously tell me I've done the right thing, four will offer support when I say I'm not standing for Westminster and explain why, and the rest will say it's creating real concerns for them." The irony is that the people who are left feeling most abandoned are the anti-sectarian, pro-agreement voters on whom the future of Northern Ireland most depends.
For them, in particular, these last days before decision time are agonising. On the one hand, since the UUP is almost certain to lose seats elsewhere, a win for Sylvia Hermon in North Down might be the only thing that saves David Trimble and rescues the agreement. On the other, a vote for the UUP will simply be totted up in the sectarian headcount.
The complex choices that may lie behind a mark on the ballot paper disappear in the crude numbers game that allows only two kinds of politics: wars within the tribes and wars between the tribes.
All over Northern Ireland, people will be faced with the same dilemma as the deadly logic of "50 per cent plus one" works its way down to private moments in the polling booth. If many people end up going for what seems the least worst option, they will also be longing for the day when they can choose the best.