President Donald Trump asked an appeals court on Monday to overrule the decision of a lower court that forced him to hand over his accounting records from before he became president. If the ruling is not overturned, Trump will have to give up key financial documents to the Democrat-controlled House of Representatives Oversight Committee.

The president’s legal team said that a May decision by U.S. District Judge Amit Mehta ordering Trump’s accounting team, Mazars LLP, to comply with the subpoena was flawed and should, therefore, be overturned. Mehta’s decision marked an important victory for House Democrats, who have been striving to find evidence that Trump either colluded with the Russians to win the 2016 election or obstructed the investigation of former special counsel Robert Mueller.

The Democrats have been trying to obtain Trump’s financial records for years ever since he announced that he was running for president in 2016. However, the New York real estate tycoon has refused to release his tax files, never giving a reason why. Instead, Trump consistently deflected, attempting to draw attention to Hillary Clinton and her “missing emails,” bringing an air of conspiracy to both claims in order to delegitimize the Democrats’ legitimate call for his records. Many analysts suggest that the files will show that Trump either evaded taxes or that he is not as rich or successful as he claims to be – or both.

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As House Democrats ramp up their calls for impeachment, Trump’s accounting records have become even more important, as some representatives believe that they will provide damning evidence that could be used to indict the president. Many liberals hope that even if Trump’s tax returns don’t show any direct evidence of collusion, they will include enough suspicious dealings with the Russians that the public and the GOP will begin to doubt the integrity of the president.