HEMPSTEAD, N.Y. — Monday night’s debate here was a tremendous victory for Donald Trump, but his performance left plenty of room for improvement.

Big picture: Polls show support for Hillary Clinton is collapsing, and she desperately needed to stanch the bleeding. She did nothing during the debate to change the trajectory of those increasingly bleak polls.

With states like Pennsylvania and Colorado in play this week, we could be talking about states like Michigan and Wisconsin in play next week. That would put the race away early for Mr. Trump.

Mrs. Clinton’s primary charge against Mr. Trump is that he lacks the “temperament” to be president. In an easy glide Monday night, Mr. Trump demonstrated otherwise.

He was perfectly presidential, even if a bit unpolished at times — just the way so many of his supporters love him. He was poised and even a bit mannerly at times.

Perhaps a bit too mannerly. But we’ll get to that.

Mrs. Clinton failed to do anything that will change the overwhelming view of her that she is slick, calculating and out of touch. And her plastic smile and that practiced, canned laugh — including a truly bizarre shoulder jiggle at one point — will only feed the notion that she is not really all there.

In addition, Mrs. Clinton failed to land any devastating punches on Mr. Trump. She landed a few potent shots about his tax proposals and his tax returns, but nothing extraordinary. And nothing anywhere near as withering as everything everybody in both parties and the media have already hurled at the guy.

From the start, the debate was lively and fiery. That was not because of the moderator, and it certainly was not because Hillary Clinton was on stage. It was entirely owing to Mr. Trump’s presence.

Something about his swashbuckling manner always puts people off kilter a little, and the result always seems to be a debate that is more robust and honest — if sometimes a bit imprecise.

As for moderator Lester Holt, he will be excoriated in coming days for his multiple follow-up questions of Mr. Trump and his failure to ask even the most basic questions of Mrs. Clinton.

She also used up a number of lines that she had obviously practice extensively — to little effect.

“I know you live in your own reality,” she said at one point, but it was entirely lost in muddle.

But here is where Mr. Trump has a lot of room to improve.

Instead of simply prosecuting the case against Mrs. Clinton, he dutifully answered all of Mr. Holt’s questions and responded to all of Mrs. Clinton’s jabs — no matter how silly.

After successfully turning questions about his unreleased tax returns into questions about Hillary Clinton’s 33,000 destroyed emails, Mr. Trump dutifully changed the subject back to his tax returns and spent far more time explaining that. Forget the tax returns and hammer away at the emails.

One of his sharpest moments came when he repeatedly hammered her for an answer on whether the economy and bad trade deals was the fault of President Obama or former President Bill Clinton.

In truth, that is the entire crux of his campaign and if he sticks with it, he will win.

He is most effective when he is reminding people that Hillary Clinton has been around on the national political stage for the better part of three decades and only now offering to fix things.

“Why are you just thinking of these solutions now?” he asked in possibly his best line.

A good runner-up was when he acknowledged that Mrs. Clinton has plenty of experience, “but it’s bad, bad experience.”

The really good news for Donald Trump supporters is that if we have learned nothing else from this election, it is that Mr. Trump is a fast learner. He was very good in this debate. He will be even better in the next.

• Charles Hurt can be reached at charleshurt@live.com; follow him on Twitter via @charleshurt.