In football it is known as "tapping up" - approaching a player from another team.
There are strict rules about it, as Chelsea's Jose Mourinho and Arsenal's Ashley Cole can tell you, even though soccer agents seem to honour them more in the breach than the observance.
In politics, the rules are even more fluid. Northern Ireland's former security minister, Shaun Woodward, for example, owes his current ministerial career to his timely conversion from Tory spin doctor to Blair acolyte.
The move would increase the UUP's ministerial quota to three
As the Ulster Unionist leader, Sir Reg Empey, told Inside Politics - every party looks around to increase its own strength, and if they approach opposition players then "so what".
"So what", maybe, when you are talking about newspaper reports of approaches to the likes of the Alliance's Seamus Close or the DUP's Mark Robinson.
Sir Reg, incidentally, would not confirm or deny these approaches, although he confirmed that his party had talked to political "colleagues" about increasing its strength.
But the "so what" argument became rather more stretched when the UUP successfully tapped up the player manager of another side, namely David Ervine of the PUP.
Those involved saw the deal as a clever move, which increased the UUP's ministerial quota to three in any restored executive, swinging the balance in favour of unionists.
But the deal's critics have portrayed it as a Faustian pact, to borrow a phrase David Trimble recently used about the Orange Order.
According to this version, the UUP has abandoned its often-touted principle of "no guns, no government" for the distant possibility of an extra ministerial car.
Ian Paisley has led the charge, and to counter his attack, Sir Reg has fallen back on the DUP's "history of ambivalence towards militant loyalism".
We have heard the names of the "UUUC", "Ulster Resistance", and the "Third Force" being intoned.
However, Sir Reg is more vulnerable to criticism from those within his own ranks who do not have any history to shrug off.
The Ulster Unionists' only MP, Lady Sylvia Hermon, expressed her "deep distress" over the move during a Commons debate when she was ambushed by the DUP.
Then the Down district councillor Peter Bowles, who played a key role in the launch of Sir Reg's leadership campaign, told Inside Politics he felt "personally let down".
This is not least because he is left with the unenviable task of trying to explain the decision to the people of Loughinisland village, who do not need reminding about the UVF massacre in the Heights bar.
New standing orders
One curious aspect is why the Ulster Unionists felt the need to declare their hand on "Day One of the Hain Assembly", given that the handout of ministerial seats may never take place.
If it does, the rules have been changed so that party strengths will be calculated on the day when any future executive is formed.
By declaring their intent on Monday 15 May, the UUP has taken a big and very real political risk for what appears only to be a semi-distant theoretical payback.
Sir Reg "is more vulnerable to criticism from within his own ranks"
Sir Reg says the late issue of the new standing orders on Friday 12 May left him with no choice.
But on 8 May, Lord Rooker gave the UUP an assurance in Parliament that the rule would be changed, an assurance which with hindsight it might have been as well to accept.
Sir Reg believes not just the DUP, but elements in the government want to stop the PUP-UUP deal.
He wonders whether this could be connected to an as-yet unpublished side deal on cutting the number of ministries or subsuming policing and justice within the current number of ministerial picks which each party will get.
Equally, it could be that a UUP-PUP pact adds an extra complication to the government's overall game plan for restoring power-sharing.
Some Ulster Unionists have tried to draw comparisons this week between their move and John Hume's decision to reach out to Gerry Adams in the early 1990s.
But despite all the unionist criticism of a "pan-nationalist front", John Hume could never be accused of putting the SDLP's partisan advantage before the party's principles.
Right now, Sir Reg must be hoping that the UVF stay quiet and hurry up their deliberations on ending paramilitary activity and starting disarmament.
If that produces results, "tapping up" David Ervine could yet pay off - if not, it could turn out to be an own-goal.