Given the alleged bad blood between Richard Holbrooke, the Obama administration’s special envoy to Afghanistan, and Hamid Karzai, the country’s embattled president, it was fortuitous that someone of John Kerry’s stature happened to be in Kabul over the last few days.

Mr Kerry’s senatorial field trip, which had been planned before this latest crisis unfolded, proved a useful accident for the White House, which was faced with the spectre that Mr Karzai would refuse to accept the logic of holding a second round run-off in the presidential election.