Few big jobs have been reviled with as much intensity as the vice-presidency of the US. Thomas Marshall, Woodrow Wilson’s veep, hated the pointless impotence of the post. He compared his role to that of “a man in a cataleptic state. He cannot move. He cannot speak. He suffers no pain and yet he is conscious of all that goes on around him.” John Adams, the very first man to hold the job, described it as “the most insignificant office that ever the invention of man contrived or his imagination conceived”. But the canny Adams also spotted its potential. “As Vice-President, I am nothing,” he wrote presciently. “But I may be everything.” Lyndon Johnson made the same point with characteristically more force. Whenever President John Kennedy came into the room, he told friends, “I felt like a goddamn raven hovering over his shoulder.”

With the presidential primary election nearing its end, the US is entering that quadrennial period when the eyes of the world turn to this critically insignificant job. It promises to be among the most important ever. That’s not because anyone expects the next vice-president to repeat the oddly exceptional role of the current one. There may have been times when people wished that Dick Cheney was in a cataleptic state, but he has been unusually engaged...

In Mr McCain’s case the choice could be especially important. He is 72 years old and would be the oldest man ever to become president. That means his vice-president must truly be ready to take the reins from day one in the job... Mr McCain is left looking for a young, experienced, capable conservative Republican, preferably with a particular gender or ethnic appeal. There aren’t too many of those about, even in America.

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