Rather than attempt to enforce the subpoena, Schiff and the other lawmakers urged Kupperman to voluntarily comply with the House’s demands.

They said he and his lawyers should, at a minimum, abide by an impending decision in a court case that involved former White House counsel Don McGahn, who has resisted a House subpoena to testify by claiming that he is “absolutely immune” from congressional demands because of his proximity to Trump.

The White House has claimed that Kupperman, too, is “absolutely immune” from testifying in the impeachment inquiry.

House lawyers indicated that they expected Kupperman and his lawyers to respond to the withdrawal of the subpoena imminently, and urged him to dismiss his demand for a judge to weigh in on the House’s demand for his testimony.

At issue for Democrats is the tight time frame that Democrats envision for the impeachment process, which top lawmakers have hoped will be completed before the end of the year. The judge in the Kupperman matter, Richard Leon, had agreed to an expedited schedule, but one that would still probably stretch deep into December or even January.