Mr. Trump has repeatedly dismissed the need for the type of “war room” structure used by aides to President Bill Clinton during his impeachment battle in the late 1990s. But others around the president are less certain that the current structure around Mr. Trump can withstand the intensity of the coming weeks.

That includes Republicans in Congress, who will be faced with voting on articles of impeachment, and who have repeatedly complained that the White House has provided little clarity on a response to Democrats. Among other potential benefits, aides to Mr. Trump hope bringing on additional personnel will placate those critics.

Mr. Sayegh, who left the administration less than six months ago to work for the firm Teneo, was pushed for the job by Jared Kushner, Mr. Trump’s son-in-law and a senior adviser, who wanted to add him to the communications team, according to three people briefed on the events. Mr. Kushner is directing key aspects of the White House response to the impeachment inquiry.

Ms. Bondi, with her legal background, has been seen by some of the president’s aides as a good choice to appear on television on Mr. Trump’s behalf. She is a personal favorite of Mr. Trump.

Their exact roles remain to be seen, including what other special projects they might work on. As special government employees, they are limited to working at the White House no more than 130 days, suggesting that the plan is not for either of them to stay on in the long term.