Scott Pruitt, the administrator of the Environmental Protection Agency, may not be in his job much longer. Over the past several weeks news reports have revealed that Pruitt installed a $43,000 phone booth at the EPA with taxpayer funds, rented a below-market condo from a lobbyist, and took an expensive trip to Morocco for a reason he still hasn’t fully explained. Normally no cabinet official could survive these scandals, and to the extent Pruitt has, it may be thanks to the intervention of White House legislative director Marc Short. The Washington Post reported Thursday that Short “remains one of the few in the administration willing to defend [Pruitt].”

Short and Pruitt are linked by more than ideology—both have close connections to the Koch political machine, which has gotten its tentacles extraordinarily deep into the Trump administration, from the middle tiers of various agencies right up to the West Wing. This week, Senate Democrats began a concerted push to get more information about these ties, which have been slowly reported out over the first year–plus of the Trump presidency.

When Pruitt faced Senate confirmation, he got a big boost from the network of political groups funded or affiliated with archconservative billionaires Charles and David Koch. A Koch Industries subsidiary spent $5.7 million lobbying in the first quarter of 2017, in part pressing the Senate to confirm Pruitt and a raft of other EPA nominees, according to a report last year from the nonprofit Public Citizen on “The Koch Government.” Twenty-three groups signed a letter to the Senate during the confirmation process urging yes votes for Pruitt, and a vast majority of those groups received support from the Kochs. This was all because Pruitt has long been a Koch man: As attorney general of Oklahoma, he coordinated with “major oil and gas producers, electric utilities and political groups” with Koch ties in order to thwart Obama-era regulations, according to a report from The New York Times last year.

In this context, Short’s strong advocacy for Pruitt now that he’s under serious fire is unsurprising: Short worked at Koch Industries as a vice president of special projects, and was also president of Freedom Partners, the main clearinghouse for Koch money in the political world. In the White House alone, there were 21 current or nominated White House officials with close ties to the Koch, according to the Public Citizen report, with Short being perhaps the most closely linked.

The same is true at the EPA beyond Pruitt as well: Samantha Dravis, the associate administrator of the EPA’s Office of Policy until she resigned earlier this month*, was the former president of the Rule of Law Defense Fund, which was funded in part by the Koch brothers. Daisy Letendre, a senior EPA advisor on policy, worked at the Koch brothers’ millennial-outreach group. The EPA’s White House liaison, Charles Munoz, was a field organizer for Americans for Prosperity, a major political outfit funded by the Koch brothers. Patrick Traylor, the deputy assistant administrator at the EPA’s Office of Enforcement and Compliance Assurance, had represented Koch refineries in court.

Senate Democrats have now taken aim at these ties and are demanding more information on whether any of these officials have coordinated policy actions with their Koch patrons. In a letter to Pruitt on April 18, Senators Sheldon Whitehouse, Edward Markey, Catherine Cortez Masto, Ron Wyden, Elizabeth Warren, and Tom Udall requested that the EPA turn over “any communication or documentation thereof (including but not limited to emails, memos, meeting notes, correspondence, and calendar items) between EPA employees” and Koch Industries or its various political outfits.

Similar letters went out to the Department of the Interior, the Office of Management and Budget, the Department of Labor, the Department of the Treasury, the Department of Veterans Affairs, the National Labor Relations Board, the Consumer Financial Protection Bureau, and the White House itself. 

On the EPA, the senators are interested in documents related to recent rulemaking on the Waters of the United States regulations and the Clean Power Plan; the Trump administration rescinded the former and put a two-year delay on the latter. Both regulatory initiatives came under furious assault from the Koch political operation when they were announced, and when the Koch-funded Freedom Partners issued a two-page “action plan” at the start of the Trump administration, repeal of both policies were prominently featured.

In a series of floor speeches this week, the senators outlined concerns that the Koch political operation was essentially becoming a shadow government. The early, post–Citizens United fears about the Kochs were that they had become their own political party—one that, in some respects, was better-funded and more highly organized than the GOP.

But those early Koch efforts were primarily about out-of-power opposition and increasing the number of Republicans in Congress. But as soon as Trump was elected, the Koch network saw an opportunity to actually staff up a federal government. “We’re happy that he’s picking people who have that free market background,” Frayda Levin, a Koch network donor, told Politico in November 2016 during the Trump transition. “Particularly because on many issues, [Trump] is a blank slate, so anybody with expertise is in an amazing position to shape his agenda.” Indeed, Public Citizen found 44 Trump administration officials government-wide that have close ties to the Kochs and their political groups.

“Of course, a Web like [the Koch’s] has its stooges and quislings, and in the Trump administration, they can get to high places,” Whitehouse said on the Senate floor Monday. “Imagine if you’ve been building this Web of Deceit for decades, and one day you get to plant your phony minions into real, high-level government positions. What wonderful legitimacy.”

A spokesperson for Whitehouse said the administration had not yet acknowledged receipt of the letters nor provided any information. The requests have a due date of May 15. It’s something the senators would like clarity on before the fall—the Koch network has already said it plans to spend between $300 million to $400 million this cycle.

*This story has been corrected to reflect that Dravis no longer works at EPA.