Donald Trump gave a speech Thursday night in Charlotte unlike any other he has delivered in his presidential campaign to date: He was measured, on message and, most surprising of all, remorseful over past mistakes.

Here's the relevant portion — although the entire speech is worth a read:

As you know, I am not a politician. I have worked in business, creating jobs and rebuilding neighborhoods my entire adult life. I’ve never wanted to use the language of the insiders, and I’ve never been politically correct — it takes far too much time, and can often make more difficult.
Sometimes, in the heat of debate and speaking on a multitude of issues, you don’t choose the right words or you say the wrong thing. I have done that, and I regret it, particularly where it may have caused personal pain. Too much is at stake for us to be consumed with these issues.
But one thing I can promise you is this: I will always tell you the truth.

That's a stunning change in tone for a candidate who has built not only his presidential campaign but also his adult life on an unapologetic brashness. It's also the start of the right message for Trump. Hillary Clinton's biggest problem in the eyes of voters is that she isn't honest or trustworthy — they think she says and does whatever is politically expedient at the moment. Trump's casting of himself as a truth-teller — albeit one a little rough around the edges — is a path back to relevance for him. The pivot — that Republicans had hoped and prayed might come — appears to be here.

Except if it's not. Or if it's already too late.

Speaking at a rally in Charlotte, N.C., Republican presidential nominee Donald Trump said that foe Hillary Clinton has "betrayed" Americans. (The Washington Post)

Remember that Trump has dangled the pivot promise before. He would regularly tell interviewers earlier this year that once he locked up the primary nomination, he would start to act more "presidential." On the night of the California primary — June 7 — Trump delivered a speech on a teleprompter that made clear he understood or claimed to understand the responsibilities of being the presidential nominee of the Republican Party. Throughout the summer, pivots have been floated by his aides — led by now-deposed campaign chairman Paul Manafort — only to be ultimately dismissed by the candidate himself.

One speech coming hard on a(nother) campaign shake-up then can't be — or shouldn't be — considered a pivot. It's like losing 10 pounds on the first five days of a diet. It's not about the initial weight loss. It's about sticking to the diet plan, which usually requires an extended commitment to changing your lifestyle. That's how success is judged.

Then there's the fact that Trump is not only badly behind in most key swing state polling but also has an image problem that makes Clinton's issues seem like small potatoes.

Not only does Trump trail Clinton 50 percent to 42 percent in the latest Washington Post-ABC News national poll, but 61 percent of registered voters have an unfavorable opinion of him — including 50 percent who view Trump in a strongly unfavorable light.

The story is the same in swing states. Trump trails Clinton by 14 points in a new WaPo Virginia poll, while the Republican nominee's unfavorable rating among registered voters is a whopping 65 percent.

Reminder: It's Aug. 19. Trump has spent almost every day since he effectively secured the party's nomination in the May 3 Indiana primary making his image problems worse, not better. The general election is in 81 days.  While people say that's ages in political terms — and they're right — it's also true that perceptions about politicians are tough to change in less than three months' time.  Especially when people feel as strongly about a candidate as they feel about Trump.

We may look back — assuming Trump can stick to the message and tone he debuted in Charlotte last night — and conclude that it was simply too little, too late. Trump has wasted well more than half of the general-election campaign on a petulant and strategy-less effort that has left him badly out-positioned heading into the fall. A single speech won't change those facts.