Cipollone sees impeachment as his domain because he views it as a legal matter and has privately complained to colleagues that Mulvaney is trying to wrest control, the people said. Mulvaney believes he’s in charge because impeachment is political and expects Cipollone to report to his office, they said.

Complicating the dispute between the officials, Mulvaney has fallen out of favor with some of the president’s allies after high-profile stumbles handling the impeachment inquiry, and Trump last month privately tested the idea of replacing him. By contrast, Cipollone enjoys the support of Trump and senior adviser Jared Kushner, positioning the lawyer to outlast Mulvaney.

The animosity between two of the highest-ranking administration officials threatens to further muddle Trump’s impeachment defense as the White House struggles to respond to a torrent of revelations in the House probe. The White House’s strategy hinges on keeping congressional Republicans unified by portraying the probe as a partisan and illegitimate exercise.