Zimbabwe has become an issue on which, as Edmund Burke put it, it is difficult to speak and impossible to be silent. But not, it seems, for Barack Obama, America's President-elect, who last shared his view on Zimbabwe in June - despite having since spoken eloquently of how, under his leadership, America would pursue its interests through “the power of our moral example.”

Nor has silence on Robert Mugabe's tyranny proved impossible for Hillary Clinton, Mr Obama's chosen Secretary of State. When asked by The Times for her views on Zimbabwe's deepening chaos, Mrs Clinton's office referred our reporter to a statement she had made in June, while still on the campaign trail seeking the Democratic presidential nomination.

Nor for Susan Rice, an expert on Zimbabwean politics and Mr Obama's new Ambassador to the United Nations. Dr Rice's experiences in Rwanda after the genocide turned her into a liberal interventionist. But not, so far, in Zimbabwe.

George Bush, the US President, yesterday echoed calls by his Secretary of State, Condoleezza Rice, for Mr Mugabe to go: “Across the continent,” he said, “African voices are bravely speaking out to say now is the time for him to step down.” But these voices - Kenya's, Botswana's - carry fury but no punch. South Africa and the African Union still favour dialogue.

Washington's president-elect has long been a stern critic of Mr Mugabe's repression. This is the moment to rebroadcast his revulsion. He has a chance to trumpet America's new moral ambition, especially in Africa. A despot as shameless as Mr Mugabe might be tempted to flaunt Mr Obama's silence as a measure of his indifference.