Now that he’s done the impossible, Donald Trump must turn his attention to the routine. With the nomination officially in the bag, it’s time to sweat the small stuff.

He woke on Day Two of his presidential convention to an avalanche of blistering headlines: “Chaos at the Convention,” a “Civil War Breaks Out” and “Melania’s Plagiarism.” The usual media suspects were predictably overheated, trying to create a sense that his coronation went off the rails.

Here’s the truth: The campaign operation remains clunky, there are some unhappy campers and a few party leaders are curbing their enthusiasm. But reports of chaos and civil war are, like a year full of reports of Trump’s demise, greatly exaggerated.

A chronic case of growing pains, complicated by the candidate’s impulsiveness, more accurately describes the facts. The mistakes are not unimportant, but they are far from catastrophic.

Consider this example: Just as the mother of Sean Smith, one of the four brave Americans killed in Benghazi, was telling the convention crowd about how Hillary Clinton lied to her while standing next to her son’s coffin, Trump was calling in to Fox News to blast Ohio Gov. John Kasich for not endorsing him. Naturally, that became competing news.

In journalism, that’s called stepping on your own good story with a bad one. In politics, it’s called amateur hour.

It’s getting late for the candidate and his team to be making rookie mistakes, but the question is how much of a penalty they will pay for not running a more professional campaign.

Trump, of course, has defied political gravity from the day he announced his candidacy, and can point to his nomination as proof that he knows exactly what he’s doing.

Moreover, by picking Mike Pence to be his running mate, he showed he can go against his own grain when he absolutely must. Such big-picture decisions matter most, and Trump, you might have heard once or twice, has a knack for closing the deal.

Still, small errors can accumulate, and enough of them can add up to big problems.

The election is likely to be very close, meaning every vote in every swing state is worth fighting for, and that requires an organization devoted to turning out all potential supporters. Leaving any vote behind would be malpractice.

It also takes targeted advertising, coordinated with the candidate’s appearances so they reinforce the same themes and messages. That kind of advertising takes money, lots of it.

So far, the Trump campaign has none of those things. It has no real focus on voter turnout and no fundraising operation consistent with modern presidential campaigns.

One glaring result is rows of empty seats in the convention galleries — usually occupied by donors, bundlers, corporate clients and lobbyists.

Trump made a loud virtue of doing without them, and a virtue it may be, but their absence diminishes the sense of an enthusiastic audience and unified party.

The empty seats also defy one of the oldest tricks in the political business — pack a small room so the crowd looks large. The less-than-filled arena is ironic given the way Trump filled major venues during the primaries.

As for the Melania goof, it’s obvious the campaign doesn’t have much of a speechwriting team, either.

The risk is that any one of these shortcomings could cost Trump two or three points in two or three swing states — and the election.

The immediate challenge is to tighten up the ship so what is said from the podium is the news of the day. Scripted events with major TV audiences will be rare after Thursday, and failing to get the usual convention bump of a few points would be a lost opportunity. With Democrats gathering next week, Hillary Clinton could build on her lead to emerge with a significant advantage.

Still, with the race now entering a new phase, Trump continues to have a very solid chance to win. The nation is eager for big change, and events, from terrorism to police assassinations and who knows what else, are likely to rattle the country all the way to November.

The candidate who responds better to the gathering crisis will be in the driver’s seat. All the more reason, then, to sweat the small stuff so the whole campaign is ready to seize victory.