"This was a larger moment for the former president, and it was a long time coming. In this one speech, he was essentially making good on a marital and political promissory note by employing the full measure of his rhetorical skills to boost his wife's history-making week as the first woman to become a major party nominee."

"In the spring of 1971 I met a girl," Clinton said, and he was off, telling the story of how they had met at Yale and how gobstruck he was by her from the first time he saw her in class, an imposing young woman wearing big glasses and no make-up, with what he called a "strength and self-possession I found magnetic".

This was the beginning, he said, of a lifetime relationship that endured "through good times and bad, joy and heartbreak".

The quality of the rhetoric aside, there has never been a speech quite like the one Clinton delivered in Philadelphia.

A husband speaking on behalf of his wife - that has been done before.

A former president speaking in support of a prospective president is also nothing new, The Washington Post wrote.

"But the combination of the two is unprecedented. A former president who wants to be first man extolling the virtues of a former first lady who wants to be president. Only the Clintons."

"Only the Clintons" applies in so many ways. Only the Clintons have been hanging around together at the top of American politics for a full quarter century. Only the Clintons can excite and then exasperate their fellow Democrats with such dizzying predictability.

"Only the Clintons (or maybe now President Barack Obama) can send the Republicans into paroxysms of rage and the deepest, darkest pools of conspiracy theorising.

"Only the Clintons can keep going and going no matter what obstacles others or they themselves throw in their way along their long and winding path."