The sudden resignation Tuesday of U.N. Ambassador Nikki Haley is still a mystery. Her departure after less than two years on the job, just weeks before the midterms, and her lack of any evident next step all raise the question of why she is going, and why now.

We have no idea if her abrupt decision was somehow connected to her ethics woes. But they are substantial, and she departs with her once-spotless reputation badly tarnished. As our watchdog group has documented, Haley has, over the course of her tenure in the Trump administration, exemplified the ethical problems that have afflicted it from the president on down. Indeed, her resignation became public a day after we filed our latest of several complaints against her, this one to the inspector general of the State Department. Her resignation letter was officially dated Oct. 3, though, several days before the complaint was filed. And we have no reason beyond proximity to wonder if her announcement was related to our complaint.

Whatever the explanation of the timing, her resignation exemplifies how President Trump's own disrespect for government ethics has spread throughout his administration. Like Scott Pruitt at the Environmental Protection Agency, Tom Price at the Department of Health and Human Services and David Shulkin at the Department of Veterans Affairs, Haley did not live up to the ethical standards her powerful, highly visible position requires.

Instead, her conduct reveals a disregard for our most basic ethics laws - in her case, ethics regulations governing gifts to officials and the Hatch Act limiting her political activity. These are not mere technicalities: They were put in place to curb the ability of special interests to influence policy through gratuities and to prevent the abuse of government positions for partisan politics. As the U.N. ambassador - as anyone holding public office should do - Haley should have held herself to a higher ethical standard and avoided any semblance of impropriety. She did not.

Haley accepted flights on private planes likely worth tens of thousands of dollars from several businesspeople who had supported her past campaigns, which could violate ethics rules and standards. In doing so, she risked creating at least the appearance that she sold access to the highest level of American foreign policy to businesses that had donated to her campaign for governor. Like Pruitt's notorious luxury condo rental that he priced at $50 a night, far below market rates, Haley reported the value of her flights on these private jets at only hundreds of dollars apiece. That strains credulity when flights on private jets routinely cost far more.

Haley could argue that these flights were given to her exclusively because of her personal friendship with each businessperson. That is, indeed, one of the exemptions to the federal ethics regulations. But there are significant reasons to doubt that argument. These were no mere social friends who gave her these flights. They were businesspeople who had donated, in total, around $40,000 to her gubernatorial campaign.

Moreover, many of her flights were on aircraft owned by the donors' companies, and it is unclear whether the executives repaid the companies for the full value of the flights. The failure to do so would make the flight cost directly attributable to the businesses, rendering the personal gift exemption void. It hardly seems that Haley chose to respect the principle (enshrined in our ethics rules) that those in positions of power should, for the good of the country's institutions, avoid even the appearance of impropriety.

Haley was also among the first of many Trump appointees to misuse their official authority to advance a partisan candidate in an ongoing election. That conduct is expressly prohibited by the Hatch Act, enacted by Congress to prevent the use of government office for political gain. She was eventually reprimanded by the Office of Special Counsel for using her official Twitter account to advocate for a political candidate. The Hatch Act is an important tool in protecting our democratic institutions from being unduly politicized - though, admittedly, protecting democratic institutions has not been high on this administration's list of priorities. By virtue of her position, Haley should have been particularly aware of the damage these kinds of transgressions can do internationally. Officials who ignore basic ethical principles harm the country's ability to model democracy to the rest of the world.

Haley's obsequious performance during her resignation announcement underscored this president's complete personal sway over his administration. She entered the job as a former adversary of Trump's, and she showed an independent streak while serving. That was not in evidence as she praised the president, sang the unseen "genius" of his son-in-law, Jared Kushner, and declared that "the U.S. is respected." The president's disdain for ethical values, which Haley has regrettably emulated, has helped make the opposite true.

While Haley may be departing the Cabinet, the miasma of corruption remains. It has become endemic, seeping out from the president himself and spreading throughout his political appointees. Not even Haley, with her once-sterling credentials, could avoid it.

There are very few who can.

- Noah Bookbinder is executive director of Citizens for Responsibility and Ethics in Washington and a former federal corruption prosecutor. Norman Eisen is a senior fellow at the Brookings Institution, chairman of Citizens for Responsibility and Ethics in Washington, a former U.S. ambassador to the Czech Republic and author of "The Last Palace: Europe's Turbulent Century in Five Lives and One Legendary House."