IN THE FINAL update of The Economist’s statistical forecast of America’s presidential election, Kamala Harris’s chances of winning rose from 50% to 56%. Her newfound lead is small enough that it can barely be called a lead at all, and it would be no surprise if Donald Trump wins by a decisive margin. But Ms Harris is widely seen to have had a stronger week to end the campaign than Mr Trump did, and the last batch of polls to enter our model bears that out.