The White House is won not by popular vote but electoral college votes taken state by state. These races are incredibly close

Spare a thought for beleaguered Pennsylvanians. During the past few weeks, they have been pummeled with $280m worth of election ads blazing on their TV and computer screens, part of an eye-popping $2.1bn spent so far on the US presidential election.

Pennsylvania is one of the seven battleground states that, when it comes to choosing presidents, can seem as revered as the seven wonders of the world. Forget Democratic California, ditch reliably Republican Texas – it is these seven states that, come 5 November, will decide the outcome of one of the most consequential elections in modern times.