Donald Trump has taken the extraordinary step of suing the chairman of the House Oversight Committee in a desperate attempt to prevent a congressional subpoena of the president’s closely held financial records.

In a filing revealed Monday morning, the president’s lawyers argue the subpoena oversteps constitutional limits imposed on Congress and charge “Democrats are singularly obsessed with finding something they can use to damage the president politically.”

Earlier this month, Rep. Elijah Cummings (D-MD) subpoenaed Mazars, an accounting firm enlisted by Trump and his company, in an attempt to get his hands on the president’s financial records. He requested documents related to Trump’s finances stretching back 10 years.

In court documents, lawyers for the Trump Organization argue that any oversight of Trump is illegitimate unless it is meant to advance a legislative interest. Meaning, they think the committee has no need to look at the president’s finances because there’s no legislation they can build off of it.

In the filing, Trump’s lawyers complain: “The Democrat Party, with its newfound control of the U.S. House of Representatives, has declared all-out political war against President Donald J. Trump. Subpoenas are their weapon of choice.”

It goes on: “Chairman Cummings’ subpoena of Mazars lacks a legitimate legislative purpose... Its goal is to expose plaintiffs’ private financial information for the sake of exposure, with the hope that it will turn up something that Democrats can use as a political tool against the president now and in the 2020 election.”

Cummings’ request came after estranged Trump lawyer Michael Cohen raised questions about whether his former boss used to inflate or deflate the true value of his financial assets to help him carry out his business dealings.

The chairman specifically requested documents related to Trump and the Trump Organization that were used in a failed attempt by the president to purchase the Buffalo Bills NFL franchise.

“Mr. Cohen produced to the committee financial statements from 2011, 2012, and 2013 that raise questions about the president’s representations of his financial affairs on these forms and on other disclosures, particularly relating to the president’s debts,” his letter to Mazars stated. “Several of these documents appear to have been signed by your firm.”

Cummings later explained: “We are following up on specific allegations regarding the president’s actions based on corroborating documents obtained by the committee, and we will continue our efforts to conduct credible, robust, and independent oversight.”

During his testimony before the Oversight Committee, Cohen said that between 2011 and 2013, he gave Trump’s financial statements to Deutsche Bank with the aim of getting a loan to purchase the Bills franchise.

According to Cohen, Trump increased his net worth from $4.56 billion in 2012 to $8.66 billion in 2013, much of it based on the addition of “brand value.” Cohen said Trump would inflate his total assets to get friendlier treatment from banks.

Mazars said last week that it “will respect the legal process and fully comply with its legal obligations.”