Toward the end of a fiery speech endorsing Hillary Clinton on Tuesday, President Barack Obama asked his pumped-up audience in North Carolina for permission to speak candidly.

"Let me be blunt. I want to be blunt. Can I be blunt?" Obama said, before appearing to make up his mind. "I'm going to be blunt."

Obama then alluded to Clinton’s struggles on the campaign trail — "you know, Hillary's got her share of critics" — before offering what he previewed as his frank explanation of Clinton’s high unfavorable ratings:

That's what happens when you're somebody who's actually in the arena. That's what happens when you fight for what you believe in. That's what happens when you've dedicated yourself to public service over the course of a lifetime. And what sets Hillary apart from so many others is she never stopped caring, she never stopped trying. You know, we're a new country, so we like new things. And I've benefited from that culture, let's face it. When I came on the scene in '08, everybody said, ‘Well, he's new.’ They don't say that now because I'm not. But sometimes we take somebody who's been in the trenches and fought the good fight and been steady for granted.

Now, it’s not clear what here exactly amounts to being "blunt." Yes, Obama is implicitly acknowledging that he was somewhat helped to the White House by virtue of being a fresh face. But he’s using that slightly self-deprecating line to ultimately bolster Clinton.

Obama is arguing that Clinton is unpopular simply because she’s been fighting the good fight for a long time — not because of the swirl of scandal around her or her husband, and not because of anything intrinsic about her personality or policy.

That theory is unlikely to be persuasive to Clinton’s Republican critics — not to mention quite a few Bernie Sanders die-hards. But it seems crucial for understanding Obama’s endorsement of Clinton, because it fits naturally with the president’s larger explanation for throwing his support behind her.

Clinton’s biggest vulnerability as the flip side of her biggest strength

In Obama’s telling, Clinton has been hammered unfairly because she’s spent so long in the public eye fighting for what she believes in.

But while the exposure of more than 30 years in politics may be Clinton’s most obvious political vulnerability, the president also maintained it’s one of the best reasons for her candidacy.

At multiple points in his speech, Obama spoke at length about just how impressed he was by the breadth and sweep of Clinton’s knowledge on a range of policy issues. At one point, he said there’s never been a more qualified candidate in US history. Again and again, Obama cited the same range of experiences held by Clinton — as first lady, as US senator, as secretary of state — that were also openings for the attacks against her.

"[Clinton] has seen up close what's involved in making those decisions. She's seen the consequences of things working well and things not working well," Obama said. "And there has never been any man or woman more qualified for this office than Hillary Clinton. And that's the truth. The bottom line is that I know Hillary can do the job."

Here’s Obama:

Sometimes we act as if never having done something and not knowing what you're doing is a virtue. We don't do that, by the way, for airline pilots. We don't do that for surgeons. But for some reason, we think for president of the United States, I don't know, who's that guy? Come on. So, as a consequence, you know, that means that sometimes Hillary doesn't get the credit she deserves. But the fact is, Hillary is steady and Hillary is true.

In Obama’s explanation, Clinton’s weaknesses as a candidate aren’t divorced from her likely strengths as a president. They’re the other side of the same coin.

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