President Trump marks his first year in the White House on Jan. 20. Since he took the oath, he's been dogged by questions about his hundreds of businesses and the conflicts of interest they pose.

In attempts to confront Trump and force him to address these conflicts, congressional Democrats, state attorneys general and watchdog groups have sued the president. So far, their cases have not advanced very far in court. A federal judge has dismissed one suit.

But there's another legal challenge to Trump, and that's coming from a lone attorney in Washington, D.C. — Jeffrey Lovitky, a solo practitioner who often sues federal agencies over complying with regulations.

Last year, he wound up suing Trump after combing through the president's personal financial disclosures. At the time, he told NPR it's not easy deciding to sue a sitting president.

"It is intimidating. I am intimidated. I mean, I would rather not be doing this," he told NPR last March.

Lovitky sued over an issue in the personal financial disclosure's list of liabilities. It's supposed to include just personal liabilities — mortgages and other debts. The lawsuit alleges that Trump commingled personal and corporate liabilities.

Among the biggest creditors on the list, Deutsche Bank is owed more than $130 million by Trump, on four loans.

Speaking with NPR last month, Lovitky said, "If the president is personally liable to Deutsche Bank, Deutsche Bank has a tremendous amount of leverage over the president, because every asset of the president could be attached by Deutsche Bank."

The Deutsche Bank loans are reported to be of interest to Department of Justice special counsel Robert Mueller as he investigates Russian interference in the 2016 presidential election and possible connections between the Trump campaign and Russia. The bank has declined to address these questions.

Lovitky filed a second lawsuit in December, naming two of Trump's top advisers, first daughter Ivanka Trump and her husband, Jared Kushner. It says that in Kushner's disclosure, information is incomplete or missing for 32 companies, raising the possibility of hidden conflicts of interest.

"We don't know which types of companies they had a financial interest in, which in turn could affect how they perform their official duties," Lovitky said.

The White House calls the lawsuit frivolous. A spokesperson said Kushner's disclosure was certified by the Office of Government Ethics. Lovitky said that's also a problem.

"I don't believe either Ivanka Trump or Jared Kushner should receive a pass for this. And that's exactly what happened," he said.

Lovitky's first hurdle in both lawsuits is the question of legal standing. In the ethics cases filed last year, the Justice Department lawyers have led by challenging the plaintiff's standing to sue.

Standing involves questions of whether the disclosure problems hurt the plaintiff, and whether a lawsuit could fix it.

"It's a tall order to establish standing," said Louis Clark, executive director and CEO of the nonprofit Government Accountability Project, which helps whistleblowers. He said if Lovitky wins the battles over standing, things will get more serious.

"For that kind of challenge to be successful, you're really going to need some legal heft," Clark said of Lovitky's lawsuits. "I would hope that he would reach out and accept help from others who see the importance of what he's trying to do."

But at least so far, Lovitky stands alone, in what he sees as a mission.

"This is something that was not planned," he told NPR. He talked about duty — he was once an Army lawyer — and his career as a D.C. attorney.

"My entire legal background is essentially litigation against U.S. government officials," Lovitky said. "That's what I have done. So it's, I guess, my duty, my obligation to do it."

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