Democrats on the House Oversight Committee on Thursday asked the Justice Department for documents related to the decision to sue to block the AT&T takeover of Time Warner, the parent company of CNN, raising concern about White House involvement in efforts to block the merger.

CNN is one of President Donald Trump’s favorite punching bags, and he openly pledged during the 2016 campaign to block the merger between the news network’s parent company, Time Warner, and AT&T, which Democrats noted in their letter to Attorney General Jeff Sessions.

Democrats on the committee asked the Justice Department for all communications related to the lawsuit and the department’s negotiations with AT&T and Time Warner, as well as any documents that note contact with White House officials on the matter.

Democrats on the committee also highlighted several other news reports that Trump himself met with AT&T’s chief executive shortly before the inauguration about the merger and that Jared Kushner met with officials at Time Warner and CNN about CNN’s coverage of Trump. The letter also notes a report that officials in the Justice Department told Time Warner that it would need to offload CNN in order to successfully complete its merger with AT&T.

“This conduct is, in our opinion, an overt and unprecedented threat to interfere inappropriately with the deliberations of career officials at the Department of Justice,” the Democrats wrote in their letter. “Their mission is to enforce the laws of this nation independently and in a non-partisan manner—not to use them as a weapon to attack press outlets that serve their constitutional functions and express criticism of the President.”

The Justice Department sued AT&T and Time Warner in November, arguing that the merger would hurt American consumers. The lawsuit fueled speculation that the Trump administration was politically motivated to opposed the merger due to the President’s disdain for CNN.

Read the Democrats’ letter to Sessions: