Melania Trump, wife of Donald Trump, waves as she arrives to speak at the Republican National Convention in Cleveland on July 18. (Mike Segar/Reuters)

Donald Trump's immigration position is, at its heart, fairly simple. People in the country illegally will be subject to deportation if he is elected president, as he said in his speech this week in Arizona. Even those who hadn't crossed the border illegally but who had been admitted on a visa and then didn't leave are "a big problem" in Trump's estimation.

"Immigration law doesn't exist for the purpose of keeping criminals out," he said. "It exists to protect all aspects of American life — the work site, the welfare office, the education system and everything else."

That speech came more than three weeks after Trump's campaign promised to answer questions about a more personal component of the immigration issue. In early August, Trump pledged that his wife, Melania, a native of Slovenia, would hold a news conference explaining how she managed to navigate the onerous process of getting a green card. He made the pledge after a number of outlets raised questions about the timeline of her entry into the country.

Remember when the New York Post ran a front-page story showing nude photos of Melania Trump? (Yes, you do.) Politico realized that the date of that shoot, 1995, put her in the United States before 1996, the year she has said she arrived on a visa. After that story came out, Melania Trump tweeted a broad defense of her arrival.

The promised news conference, though, hasn't yet happened.

Curious about the extent to which marrying an American citizen washed away any previous immigration problems, I reached out to David Leopold, an immigration attorney from Cleveland and former president of the American Immigration Lawyers Association. He explained that the popular understanding of how immigration is linked to marriage is wrong — but also noted a number of other questions worth asking about Melania Trump's arrival in the United States.

To the marriage question first. The understanding in popular culture that marrying a U.S. citizen automatically grants citizen status is incorrect. "The act of marrying a legal permanent resident of the United States doesn't in and of itself do anything," Leopold said.

There are three main ways in which someone can get a green card: through an employer, through an immediate relative or through the green-card lottery. What's an immediate relative? A son or daughter — or a spouse, for example. Essentially, then, a potential immigrant goes from having no immediate relative (and having to hope to win the green-card lottery) to suddenly having one — and for that group, there is no quota on how many green cards can be issued. A green card isn't guaranteed to the new spouse, but it makes them eligible to begin the process.

It isn't guaranteed, in part, because there are restrictions on who can receive a green card. It is not the case, for example, that an immigrant who enters the country by illegally crossing the Southern border can simply marry an American citizen and be granted a green card.

"If I marry somebody who is undocumented, the only way at this point she is going to get a green card is if she lawfully entered the United States originally," Leopold said. "If the person entered the country without inspection — I married a woman who crossed the border or entered through fraud or something like that — then she is ineligible to get a green card in the United States." There are exceptions that apply, but this is a critical point: If someone committed fraud or entered the country illegally, they cannot get a green card unless they receive a waiver for doing so.

This is important to the question of Melania Trump.

Here's how she explained getting her citizenship, to Harper's Bazaar:

I came here for my career, and I did so well, I moved here. It never crossed my mind to stay here without papers. That is just the person you are. You follow the rules. You follow the law. Every few months you need to fly back to Europe and stamp your visa. After a few visas, I applied for a green card and got it in 2001. After the green card, I applied for citizenship. And it was a long process.

According to Leopold, the need to have to travel back to her home country wouldn't accompany a visa linked to employment, in his experience.

"The only time I've seen that — and I've been doing this a long time, and I've compared notes with other immigration lawyers — that the coming in and going out, to anybody who's been around this stuff, suggests that she was on a visitor visa, which doesn't permit work," he said. If Melania Trump came in on a visitor visa and began working over a short period of time, the government would assume that she entered the country fraudulently. If she told a customs official she was entering the United States as a visitor but was planning to work, that's a material misrepresentation.

To get a work-related immigrant visa, Leopold added, Trump's prospective employer would have had to prove that Trump filled a job duty that no American could fill — to show, in other words, that no other model in New York City would have done that shoot. Unless, of course, she had special skills — or a special degree.

You may remember that shortly before questions about Trump's status arose, she suddenly took down her personal website. That change followed revelations that Trump claimed to have a degree that biographers from Slovenia discovered she didn't.

"At the age of eighteen, she signed with a modeling agency in Milan. After obtaining a degree in design and architecture at University in Slovenia, Melania was jetting between photo shoots in Paris and Milan, finally settling in New York in 1996," the site read. The part about the degrees, it seems, was not true, as our fact checkers noted.

We don't know why Melania Trump claimed to have that degree — but having such degrees could bolster an argument for a work visa. If she told an employer she had degrees she didn't to obtain a visa (and the employer wasn't the wiser), Melania Trump is culpable.

Again: It's not clear what visa Trump used to enter the country and how it related to her work experience — but she asserts that she has always been in full compliance with immigration laws. If that's not true, it's a problem.

"The bottom line is, if you have procured or attempted to procure an immigration through fraud or misrepresentation, you are inadmissible to the United States, and you need to be admissible to the United States to get a green card," Leopold said. Fraud "always is part of your immigration portfolio," he added, saying it "sticks to you" — meaning that leaving and reentering properly wouldn't absolve previous missteps. Nor would being married to a citizen.

"If there were material misrepresentations or fraudulent representations regarding her work or her intent to work if she came in on a visitor's visa, that would implicate the validity of her green card," Leopold said. "And that would then affect her citizenship, because when you apply for citizenship, one of the questions they ask you is if have you ever sought to obtain immigration benefits from fraud. If you don't 'fess up and answer 'yes' if you've done that, now you have bad moral character and you're ineligible for citizenship." In the worst case, this could lead to denaturalization — loss of citizenship.

How Melania Trump obtained her green card is another question.

In an interview with Univision, a former attorney for the Trump Organization said that Melania Trump obtained her green card in 2001 "based on marriage." But she married Donald Trump in 2005 and has said that she wasn't married previously.

As noted above, marriage is a fast track to green-card status, but it also carries another benefit. Someone who entered the country fraudulently isn't eligible for a green card unless they get a waiver. In this case, that waiver would have to come from a close relative — such as a spouse — arguing that an exception should be granted because the relative would suffer an "extreme hardship" if the application were refused. This is "tough to do," Leopold said, suggesting that it demands proof of legitimate economic or emotional difficulty that would result.

For Leopold (who, we will note, donated to the Hillary Clinton campaign in March), the point isn't that Melania Trump entered the country and obtained citizenship under false pretenses. To some extent, the point is that we don't know her story — which is strange, since it should be fairly simple to explain.

More broadly, though, Leopold sees this as a missed opportunity for Donald Trump as a candidate.

"To me what this shows is this broken immigration system — I know that's a cliche already — forces good people to do things they ordinarily wouldn't do. Such as cross a border without authorization, such as misstate the purpose of their trip," he said. "Clearly immigration touches his own family very directly. If this is true, then Donald Trump has missed an important opportunity to reach out to immigrants and say, 'I understand how difficult and dysfunctional this system is, and I want to stand with you, and I want to fix it.'

"But he's gone the other way."