Washington — A federal judge sided with a Democratic-controlled congressional committee on Monday, ordering President Trump's accounting firm to comply with a subpoena and turn over his long-sought financial records.

"It is simply not fathomable that a Constitution that grants Congress the power to remove a President for reasons including criminal behavior would deny Congress the power to investigate him for unlawful conduct — past or present — even without

formally opening an impeachment inquiry," U.S. District Court Judge Amit Mehta wrote in a lengthy opinion Monday afternoon.

Before boarding Marine One for a campaign rally in Pennsylvania Monday night, the president said the decision was "crazy" and "totally wrong." His attorney, Jay Sekulow, said he "will be filing a timely notice of appeal" with the court.

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The decision is likely to escalate the showdown between Democratic lawmakers and the White House. Mehta, of the D.C. District Court, ruled in favor of the House Oversight Committee and its subpoena calling for Mazars USA LLP — a firm which has handled the president's accounting — to disclose Mr. Trump's financial records dating back to 2011. He said the president and his lawyers could not prevent the accounting firm from complying with the panel's request.

"Applying those principles here compels the conclusion that President Trump cannot block the subpoena to Mazars," Mehta added in his ruling.

Rep. Elijah Cummings, the Democratic chairman of the Oversight Committee, called the ruling "a resounding victory for the rule of law and our Constitutional system of checks and balances."

Mehta, nominated by President Obama in 2014, disagreed with the argument by the president and his legal team that the subpoena by the Democratic-led panel lacked any "legislative purpose" and was part of a politically motivated ploy to undermine Mr. Trump's presidency. He cited the committee's "consideration" to bolster ethics and disclosures laws, and its investigation into whether the president has violated the Foreign Emoluments Clause in the Constitution through his businesses empire, now operated by his sons.

"These are facially valid legislative purposes, and it is not for the court to question whether the Committee's actions are truly motivated by political considerations," Mehta wrote.

The subpoena issued to Mazars has precipitated one of several legal clashes between House Democrats and the president's legal team and White House counsel — who have vowed to defy most of Democrats' subpoenas.