The investigation by Special Counsel Robert Mueller into the Trump campaign’s involvement in the Russian attack on the U.S. election system has garnered significant attention. But, more quietly, another effort to limit foreign influence over our government continues apace.

On Wednesday, a federal district court in New York will hear arguments in Citizens for Responsibility and Ethics in Washington v. Trump, in which the plaintiffs argue that President Donald Trump has violated the Constitution’s Foreign Emoluments Clause, an anti-corruption clause that prohibits government officials from receiving anything of value from foreign governments without the consent of Congress. While these cases are just beginning, the ongoing investigations into Trump’s ties to Russia have made clear that the problem of foreign influence in this administration is both very real and very dangerous.

Citizens for Responsibility and Ethics in Washington v. Trump is one of three cases that have been brought against Trump alleging he has violated the Foreign Emoluments Clause. Two of the suits also bring claims against Trump for violating the Domestic Emoluments Clause, which prohibits the states or the federal government from making payments to the president. The cases cite a wide range of instances in which Trump has received economic benefits from foreign governments without congressional consent, including payments from a significant number of foreign government officials who have frequented the Trump International Hotel in Washington, D.C., and numerous trademarks that China granted Trump after his inauguration. And these are just the tip of the iceberg: Trump’s foreign conflicts of interest are legion, spanning the entire globe.

The possibility of foreign influence over this president and his administration should raise immediate red flags. Revelations over the past nine months have shown the threat to our democracy posed by powerful officials receiving foreign payments. In the case of two prominent members of Trump’s team, the possibility of foreign influence has raised legitimate and troubling questions about whether they were acting in America’s interest or that of their foreign backers.

Consider Michael Flynn, Trump’s disgraced former national security advisor, who was forced to resign less than a month into his tenure after it was revealed that he had lied about discussing sanctions with the Russian ambassador. After Flynn left the White House, it came to light that he had been paid more than half a million dollars by a Turkish-American businessman to work on behalf of the interests of the Turkish government at the same time he was also working on the Trump campaign. While Flynn did not publicly reveal these payments during the campaign or during his time in the White House, he was forced to register with the Department of Justice as a foreign agent lobbying on behalf of the Turkish government after he resigned from his White House post.

Much of Flynn’s paid work on behalf of Turkey focused on investigating Fethullah Gülen, a political opponent of the Turkish president who lives in the United States. In one meeting in September 2016, Flynn and Turkish government officials reportedly discussed covertly moving Gülen from the United State to Turkey to avoid extradition requirements. On Election Day, Flynn published an opinion piece attacking Gülen. Most seriously, Flynn’s involvement with Turkey may have had ramifications for U.S. national security policy. In January 2017, prior to officially starting his post but after he was designated as the incoming national security adviser, Flynn delayed an anti-Islamic State military effort that had been opposed by the Turkish government. While no evidence has been revealed that Flynn received any payments to take that specific action, the previous payments raise serious questions as to his motivations—especially considered that the Trump administration went forward with the effort shortly after Flynn’s resignation.

Similarly, Trump Campaign Chairman Paul Manafort may have been compromised by foreign payments. In the mid-2000s, he entered into a secret $10 million annual contract with the Kremlin-linked oligarch Oleg Deripaska to influence Western politics to assist Russian President Vladimir Putin and his government. Recent news reports suggest there was at least a $60 million relationship between the two men over the last decade, including a millions of dollars in questionable loans to companies linked to Manafort. In 2012 and 2013, Manafort was paid at least $17.1 million to work for a Kremlin-aligned political party in Ukraine. As he rose to prominence in the Trump campaign during the summer of 2016, he asked an associate how he could use his newfound fame and power to “get whole” and then sought to set up a private briefing with Deripaska, to whom he owed millions of dollars after a failed business deal. And just a few days after that, the Trump campaign made its only change to the Republican Party platform, weakening an anti-Russian provision.

But the problem is broader than those who surround Trump; the president himself has a history of questionable payments that seem aimed at influencing the actions of government officials. In 2012, two of the president’s children, Ivanka and Donald Jr., faced possible felony fraud charges for misleading prospective buyers of units in the Trump SoHo hotel and condo development. Then, their father’s personal attorney, Marc Kasowitz, went to meet with Cyrus Vance, the Manhattan District Attorney. Kasowitz had donated $25,000 to Vance’s campaign earlier that year. (Vance did, however, return that money prior to the meeting.) Three months after the meeting, Vance overruled his prosecutors and declined to press charges against Ivanka and Donald Jr.; less than six months later Kasowitz made a larger donation and helped fundraise for Vance’s campaign, bringing in more than $50,000 in all.

This was not an isolated incident. In 2013, New York sued Donald Trump for fraud related to Trump University. Similar complaints had arisen in Florida, and while the state was considering whether to join the lawsuit, Trump’s foundation made a $25,000 donation to a political action committee supporting the re-election of Florida Attorney General Pam Bondi. Bondi decided not to act on the complaints or join the lawsuit.

Trump’s public comments likewise reflect an unprecedented comfort with corruption and pay-for-play schemes; he has repeatedly discussed the influence his political donations have over politicians. He has bragged that, “When you give [to politicians], they do whatever the hell you want them to do.” Trump has also been hugely critical of the Foreign Corrupt Practices Act, a post-Watergate reform to prohibit bribery of foreign officials by U.S. companies, calling it a “horrible law.” In 2012, he said of the legislation: “It puts us at a huge disadvantage.”

Taken as a whole, Trump’s sordid past and current foreign entanglements are cause for grave concern. He’s been clear about his willingness to trade money for political favors, and his worldwide business holdings provide ample opportunities for him to do so. Less than a year into his presidency we have seen multiple instances of undue foreign influence at the highest level of Trump’s campaign and administration. This endangers our national security and undermines our sovereignty. It was exactly this risk that caused the framers to include an Anti-Corruption Clause in the Constitution, and exactly why this constitutional provision and the cases seeking to enforce it are so important today.

Sam Berger is the senior policy adviser at American Progress.