Unionist election pact: Winning a seat is not quite as simple as adding two sets of voters together
The DUP and Ulster Unionist pact should secure North Belfast for the DUP - although that was never too much in doubt.
And it gives the UUP a clear run at Fermanagh and South Tyrone, where Michelle Gildernew of Sinn Fein won by just four votes in 2010.
The most glaring omission, however, is South Belfast, where both parties will be up against SDLP leader Alasdair McDonnell.
The fact that they managed to combine against Naomi Long in East Belfast, though she is personally pro-Union, but not against the nationalist leader, shows how difficult this agreement has been.
The plan is that by giving unionists only one candidate to vote for then that candidate is more likely to be elected. Yet we do not yet know what other parties are standing. Nominations don't close until April 9, so there could well be a Progressive Unionist candidate or other unionists standing in some of these seats.
Bill White of the polling company LucidTalk said: "The effective deal is Fermanagh and South Tyrone for North Belfast. The others are not so important, and Newry and Armagh is a very long shot."
Unionist votes don't generally combine terribly smoothly. Joint candidates often get less than the two parties running separately. The DUP has argued that the best chance of getting people out to vote where there wasn't a sitting unionist MP was to pick someone popular from outside the party system. They felt this would minimise inter-party rivalry. Stephen Gault, an Enniskillen bomb survivor with very good contacts across the community, was amongst those approached in Fermanagh & South Tyrone. He refused to stand against Tom Elliott, the UUP candidate, and is now expected to support him.
UUP votes do not automatically go to the DUP. In East Belfast the UUP candidate is Chris McGimpsey - but since his party is now encouraging support for Gavin Robinson of the DUP he may stand down now.
Mr McGimpsey is on the liberal, perhaps even Left wing of unionism. By offering a moderate unionist option, he might have taken as many - or even more - votes from Alliance as he would from the DUP. In an interview in this paper on Monday, Gavin Robinson said he didn't think a deal was necessary.
UUP leader Mike Nesbitt spoke of a once in a lifetime opportunity to win Newry and Armagh, but Sinn Fein got 42% of the vote in the last Wesminster election and 40% in the 2011 Assembly elections, so he is being optimistic. Now the SDLP reckon they have a good candidate in Justin McNulty, a GAA star from Mullaghbawn with some support across the community. The main effect of the pact in Newry and Armagh may be to stop unionists voting tactically for McNulty to keep Mickey Brady, the Sinn Fein candidate, out.