The Kentucky and Oregon primaries moved Barack Obama closer to the Democratic presidential nomination, but did not seal his victory. He passed what his campaign insisted was an important milestone: whatever happens in the three remaining primaries, he is now assured of a majority of the party’s elected delegates. Unelected super-delegates, whose support he also needs to clinch the nomination, continue to move his way. But a gap remains. Conceivably, Hillary Clinton might recruit enough super-delegates to overtake her rival.

Though expectations are running more powerfully than ever in Mr Obama’s favour, arithmetically it remains a close race. This week Mrs Clinton added a landslide victory in Kentucky to her recent drubbing of Mr Obama in West Virginia. Mr Obama added delegates nonetheless, and then won comfortably in Oregon. But he must be disturbed that Mrs Clinton’s support shows no sign yet of fading. Everybody in the US is convinced he must win the nomination – with the exception of the indefatigable Mrs Clinton and roughly half of the Democratic party’s likely voters.