They argue that effective security measures are the essential backcloth to pursuing progressive policies.This week Peter Hain, leader of the House of Commons, suggested that Liberal Democrat and Conservative opposition to the government's plans for dealing with terrorism and crime meant that people would be safer under Labour.
But is it real, or is it just the backcloth to yet another fantasy?
That issue provided the backcloth for most of the other discussions, such as whether more money can be spent on the NHS, or whether tuition fees should be cut.
A skeletal Georgian cross frames the stage, a white chapel dominates the backcloth; the staging has the formality of a morality play.
But it was a perfectly logical thing for me to do in the wake of the MPs' expenses scandal, which was very much a backcloth to the creation of this government that people have quickly forgotten.
In the north-east, in Erzurum and Kars, where I now go, the poverty may be slightly less grinding, but the sense of being on a frontier is if anything even stronger as is a renewed and unattractive spirit of Turkish nationalism.Erzurum is the sinister backcloth to John Buchan's "Greenmantle", set in the first world war.
The cloth to be printed is spread on the rubber, either gummed in position or pinned to a backcloth attached to the table.
The new box settings (three solid walls to suggest a room instead of the traditional side wings and backcloth arrangement) began to be used in Edwin Booth's theatre from 1869, after which realistic staging became increasingly popular.
Realism found its way into domestic dramas, too, one of the earliest innovations being the box set that replaced the perspective backcloth and wings depiction of a room with three solid walls and a ceiling.
And so did so many visitors, charmed by the beach volleyball at Horse Guards Parade and the equestrianism ridden out against the backcloth of Greenwich Palace.
With no ado, a union official steps to the podium in a ballroom of the Sheraton hotel, a stars and stripes to one side and the colours of the Association on a backcloth behind, and booms: "It is my honour and distinction to welcome Donald J Trump".
