Last week, Cameron arranged a secret meeting with his party and the two Ulster Unionist parties in an effort to get some Orange votes in his corner if the next British election is close.
Cameron's move instantly aroused deep suspicions among nationalists who have seen this game before, where Unionist votes are traded for pro-unionist policies in Northern Ireland.
Cameron appears to be willing to put the North's fragile peace process at risk in order to find some grubby votes among unionism to bolster his number of seats in the next election.
He is playing with fire. There is a long and sad history of the Orange card in Northern Ireland politics. Successive Labor administrations have done an excellent job of maintaining relations with both sides in Northern Ireland and never appearing to tip too much one way or the other.
That is what is needed to put together a settlement which has survived all efforts to bring it down.
Now the DUP are strengthened in their belief that if they hold out against Sinn Fein and the devolving of justice and policing to Northern Ireland, they will get a better deal under Cameron.
Instead, Cameron may find his first order of business, if he is elected, to be a massive crisis in the Irish political process and possibly its disintegration.
Is a few Unionist votes really worth all that much to him? History would suggest the answer may be yes. It would be an act of the most awful political folly.