Chinese officials and analysts are struggling. A woman who has never visited China and who has only briefly met its leader, Xi Jinping, has suddenly emerged as a serious contender in the race for the White House. The Democratic Party will gather this week to celebrate the nomination of Kamala Harris as its presidential candidate and her selection of Tim Walz as her running mate. For China’s rulers the ascent of the Harris-Walz ticket creates two difficulties. It challenges China’s nihilistic interpretation of American politics as racist and decrepit. And it has triggered a scramble to assess how a Harris administration might approach China relations, not least because Ms Harris’s credentials on dealing with China are limited, while Mr Walz has more experience of China than any vice-presidential candidate in decades.