Democracy's Hidden Guardians:

[Mr.Bee]

2. as mentioned in the article;

"Probably the best-known shadow cabinet is the one that forms in the UK every time a new government is formed. The first formal UK Shadow Cabinet is generally credited to the Labour Party, although the concept had existed in more informal forms earlier."
...
"Apparently, somebody on Team Trump was listening. Or they copped the idea from the same place I did: the UK, Canada and Australia, all countries where the party out of power assembles a “shadow government” with a “shadow cabinet” that regularly informs voters of how and why they’d run the government differently were they in power. "