As someone who has attended Bernie Sanders rallies and written about his impressive candidacy, I expected him to prevail in the Milwaukee debate. But Hillary Clinton prevailed by going to the mat for her former boss.

Early in the debate, Vermont Sen. Sanders took the early lead on Wall Street and Clinton’s connections to that group. But Hillary Clinton climbed back in it pointing out the discrepancy between Sanders’ claims of opposition to regime change and his record in voting for it.

Claiming “it was unanimous” didn’t help Sanders’ case. So it came down to the wire, with both evenly matched. Then both candidates were asked to name good examples of leaders.

Sanders mentioned FDR and Winston Churchill. Clinton noted FDR and Nelson Mandela briefly, but pivoted to a defense of President Barack Obama, adding that Sanders had criticized the Democratic President. It was the first time I had ever seen Sanders rattled.

Clinton claimed, “Today Senator Sanders said that President Obama failed the presidential leadership test. And this is not the first time that he has criticized President Obama. In the past he has called him weak. He has called him a disappointment. He wrote a forward for a book that basically argued voters should have buyers’ remorse when it comes to President Obama’s leadership and legacy.

“And I just couldn’t agree — disagree more with those kinds of comments. You know, from my perspective, maybe because I understand what President Obama inherited — not only the worst financial crisis but the antipathy of the Republicans in Congress — I don’t think he gets the credit he deserves for being a president … who got us out of that … put us on firm ground, and has sent us into the future. And it is a — the kind of criticism that we’ve heard from Senator Sanders about our president I expect from Republicans. I do not expect from someone running for the Democratic nomination to succeed President Obama.”

Sanders responded, “Madam secretary, that is a low blow. I have worked with President Obama for the last seven years … So I have voiced criticisms. You’re right. Maybe you haven’t. I have. But I think to suggest that I have voiced criticism, this blurb that you talk about, you know what the blurb said? The blurb said that the next president of the United States has got to be aggressive in bringing people into the political process.”

Clinton noted that Sanders had gone so far as to suggest that Obama should have a primary opponent when the president sought reelection in 2012. Sanders replied that Clinton ran against Obama in 2008, but he got tepid applause at best for that last line, because voters recognize that Hillary Clinton was running for president in 2008, not trying to stop Obama.

But by calling for a primary opponent for Obama in 2012, that was a different story, one which could have sunk the Democratic Party’s chances. Nothing takes out a president like a primary opponent.

Sure, Sanders didn’t slam Obama personally in his foreword to the Bill Press book “Buyer’s Remorse,” but the book blasted Obama, and Sanders had to know what the book was about. If not, he should have asked at least. But he didn’t.

Clinton is right on this one. Obama took plenty of abuse from Republicans. The last thing Obama needed was friendly fire when trying to muster support for initiatives that Sanders otherwise claims to support.

By making the nomination a referendum on Obama, Secretary Clinton should shore up her support among Democrats who realize what the president has done for the party, instead of those who complain he didn’t do anything for Democrats.