PHILADELPHIA — It was hard to imagine that Bill Clinton could make as powerful a speech on behalf of his wife as he did on behalf of Barack Obama four years ago.

Advocating Obama’s re-election required an extended argument about public policy, a persuasive mobilization of facts and figures, and a series of pokes at the Republican Party. Few politicians are better at such things than Clinton.

Encouraging the country to see Hillary Clinton as he does was something else altogether. A policy speech wouldn’t do. And let’s be honest: Thanks to his own shortcomings and misdeeds, their relationship has involved one of the most painfully public marriages in the history of American politics.

Well, Bill Clinton managed a successful walk on the rhetorical high wire once again. The very first line was risky given the back story, but it was a grabber and unlike any ever heard at a convention before: “In the spring of 1971, I met a girl.”

And off he went, telling twin tales of how he persuaded her to marry him and how she spent her life being “the best darned change maker I have ever met in my entire life.”

He spoke of her work on behalf of poor children, African-American children kept out of schools and imprisoned with adults. He spoke of her political conversion from the party of her youth: “Her support for civil rights and her opposition to the Vietnam War compelled her to change parties and become a Democrat.”

In what is certainly a first at a Democratic convention, he invoked two of the most controversial Republicans of his time, Tom DeLay and Newt Gingrich, as character witnesses for her.

But he also spoke of her personal side, particularly her love and devotion as a mother who did the practical and selfless work all good mothers do.

He summarized the theme of a night designed to encourage Americans to take another look at his wife and to pay attention to the stories told by people who know her. Her virtues were such, he argued, that defeating her required her opponents to get voters to ignore the actual content of her character.

“Your only option is to create a cartoon,” the former president said. “Cartoons are two-dimensional. They’re easy to absorb.” This was a plea for voters to put the cartoon aside.

What was he up to? The clue came from the “Change Maker” signs waved by the Democratic crowd. It was a phrase he used over and over, sending a message to Bernie Sanders’ supporters that she was, at heart, one of them; and to voters tempted by Donald Trump, that the woman with decades of political experience was the candidate more likely to produces the changes they would welcome.

It reflected her campaign’s understanding that this is a year in which a significant share of the electorate wants something different.

For Bill Clinton, this might well be seen as the most important and most challenging speech of his life. His career helped Hillary Clinton create her own opportunities. But his mistakes not only brought her great pain but also remain a drag on her popularity. This was his explanation for why they still love each other and his case for why the young woman he met all those years ago is as impressive today as she was when he first decided he had to marry her. It was a hard thing to do in public, but it was undertaken by a man who has always thrived in the spotlight.

Clinton haters, and there are a lot of them, no doubt hated the speech. Clinton’s supporters, in the hall and in the country, were mesmerized, moved and inspired. And the swing voters? Only the pollsters can tell us for sure, but I’d be very surprised if Bill Clinton’s efforts failed to get them at least to give his wife another look, to be interested in going beyond what they think they know about her, and to consider the testimony of those who know her best.

E.J. Dionne’s email address is: ejdionne@washpost.com. Twitter: @EJDionne.