In a press conference Wednesday, Donald Trump openly called for a foreign power to obtain emails written by Hillary Clinton when she was secretary of state.

Observers across the political spectrum were horrified. Clinton’s campaign said Trump had "actively encouraged a foreign power to conduct espionage against his political opponent." Even Paul Ryan had to release a statement clarifying that "Putin should stay out of this election."

Trump’s statement is impossible to defend on the merits. But it’s actually really easy to understand why he made it: Donald Trump hasn’t been in the news yet all week.

For the past two days, the press has been covering the Democratic National Convention in Philadelphia. The news out of Philly hasn’t all been rosy for Clinton. (In fact, it’s revealed that, at least in some respects, the Democratic Party is more ambivalent about its nominee than Republicans are about Trump.)

But Trump doesn’t care whether the news is good or bad for him if he’s not in it. And if Trump is in the news, he doesn’t think the news can ever be bad.

Donald Trump truly does believe that "all publicity is good publicity." He admitted it last week when his wife was accused of plagiarizing her convention speech from Michelle Obama. It’s how he’s conducted his entire career.

"One thing I’ve learned about the press is that they’re always hungry for a good story, and the more sensational the better," he wrote in The Art of the Deal in 1987. "If you are a little different, or a little outrageous, or if you do things that are bold or controversial, the press is going to write about you."

What, exactly, "the press is going to write" is of secondary concern to Trump. Despite his whining on his Twitter account about "unfair" coverage from certain news outlets, it’s clear that the worst thing for Donald Trump is not to be written about at all.

"All press is good press" is Trump’s campaign strategy in a nutshell

Trump’s ability to get free media isn’t just a personal point of pride; it’s an important part of his presidential campaign strategy.

Trump won the Republican presidential nomination by doing basically none of the things candidates are supposed to do to turn out voters. He simply relied on the media he was getting, and the excitement of his rallies, to inspire supporters to turn out to caucuses and primaries.

And when he was running against 17 other Republicans for the nomination, all of whom were struggling to differentiate themselves from each other among a small group of core supporters, that strategy worked.

Now he and his campaign seem to think that the general election — with (essentially) only two candidates to split the vote between — will work just the same way.

Early this summer, Trump was doing an embarrassingly poor job of raising money for himself and the Republican Party — but he and his allies waved it off by saying that Trump would get so much free coverage they wouldn’t need the money anyway.

Given that Hillary Clinton is currently spending more than $10 on TV ads to every $1 spent by Trump — and yet is only a few points ahead of him in the polls — it might seem like Trump is right. At least until you realize that presidential campaigns usually do things in addition to media and advertising to turn out voters. In a general election, those things actually matter.

In 2012, Mitt Romney’s campaign was very proud of their ability to "win" the news cycle — more often than not, the story the press was talking about was good for their candidate or bad for President Barack Obama. But when it came to turning out actual voters (who probably weren’t paying attention to political media all summer), Obama had a sophisticated targeting and GOTV operation, and Romney had a thin database and a buggy GOTV app.

The Trump campaign is betting that because Donald Trump is not Mitt Romney, media will matter in 2016 where it didn’t in 2012. They might be right (especially because, thanks to the efforts of the Republican National Committee over the last four years, the party’s get-out-the-vote infrastructure is less of an embarrassment). After all, it sure seems like more people are paying attention to this presidential election months before it happens, and Trump is a big reason why.

The biggest flaw in Donald Trump’s press strategy is Donald Trump

There are a couple of problems with this strategy.

First of all, campaign "gaffes" do sometimes matter — when they confirm the impression that voters already have of a candidate.

The impression voters have of Donald Trump is that he’s a loose cannon. Sixty-one percent of Americans say Trump doesn’t have the temperament and personality to be president; 58 percent say he’s unprepared to lead. This was in a poll, by the way, that had Trump and Clinton tied at 42 percent.

At very least, the overwhelming majority of people who don’t already support Donald Trump think he’s temperamentally unsuited to the job. Continuing to make ever more outrageous off-the-cuff comments certainly doesn’t repair that impression; instead, it fixes it in place.

While presidential elections generally aren’t won or lost on the strength of candidates or campaigns, there’s definitely a point at which a campaign or candidate is such a disaster that he turns off voters who’d otherwise support him or his party.

We won’t know for sure until Election Day whether Trump is at that point, but between his total lack of interest in campaign infrastructure and his refusal to believe that anything he says could ever hurt him with voters, he certainly isn’t trying to avoid it.

The other problem for Trump — and perhaps the most important one — is that he doesn’t appear to understand that there’s an opportunity cost to dominating the news cycle with his own comments. The stories he’s crowding out might be things that reflect better on him, or more poorly on Clinton, than whatever he said to a reporter that day.

It’s one thing to believe all publicity is good publicity; it’s quite another to believe that all publicity is equally good. But that’s exactly what Trump appears to think.

Take the controversy over Melania Trump’s partially plagiarized speech at the Republican National Convention — when Trump’s publicity machine steamrolled not his opponent’s convention, but his own.

The scandal sucked up an entire day of news coverage — first the speech itself, then the campaign’s increasingly ridiculous defenses of the speech, then trickled-out leaks from within the campaign about how the speech had been written and who was to blame.

If Melania had delivered a normal, original speech, the next day’s news coverage would still have been about Donald Trump.

The headlines would have been about Trump’s formal nomination (which didn’t get as much press attention as Clinton’s partly because he didn’t make history, but also in part because everyone was still talking about Melania). Or they might have been about whether the first night of Trump’s convention was as impressive a showpiece as Trump himself had promised it would be. Heck, they might have been about how Trump’s convention speakers had focused on Hillary Clinton’s untrustworthiness — a weak point with voters.

Any of those scenarios would have been better for Trump than a plagiarism scandal. But Trump doesn’t appear to see "better."

The irony, of course, is that he is stepping on his own messaging. Trump himself understands that it’s important to remind voters that they think Hillary Clinton is untrustworthy. That’s why he calls her "Crooked Hillary." But the press has actually spent less time talking about Clinton’s untrustworthiness than they would have if she were facing someone other than Trump.

Every time Clinton’s lack of trustworthiness makes the news — say, when FBI Director James Comey called her handling of her private email server "extremely careless" — Trump has done something to make himself the center of attention again. Comey’s press conference was partially overshadowed, for instance, by the Trump campaign’s attempt to defend Trump’s use of an anti-Semitic Twitter meme three days earlier.

Trump and his campaign could have shut up and let Crooked Hillary grab all the headlines. But they didn’t, because Donald Trump can’t understand that not all publicity is equally good publicity.

Watch: The history of the GOP