Donald Trump’s extraordinary and unsubstantiated accusation that Barack Obama ordered the tapping of his phones before the November election raises three possible scenarios, each of which have serious implications for his young presidency.

The first is that Mr Obama illegally ordered surveillance on the Trump campaign. The second is that the FBI obtained a warrant for surveillance from a special intelligence court (Fisa), implying some level of evidence of contact between Trump associates and Russian officials. Either, according to Lindsey Graham, a South Carolina Republican senator, would amount to “the biggest scandal since Watergate”. Mr Graham has vowed to ascertain the truth about what he described as “earth-shattering” charges.

Larry Sabato, a University of Virginia politics expert, alluded to the third scenario — that Mr Trump was once again making up facts — saying: “Claiming Obama bugged him is an extremely serious charge. Trump needs to put up or shut up.”