WASHINGTON — Treasury Secretary Steven Mnuchin plans to hire Monica Crowley, a longtime Fox News commentator, as his top communications official, according to a person familiar with the matter.

Ms. Crowley would succeed Tony Sayegh, who has been planning for several months to leave the Treasury in May. Her hiring would be another sign of the symbiosis between the Trump administration and Fox News, a launching pad for current White House officials and a place to land for those who leave. Mr. Sayegh is a former Fox News contributor.

While the Treasury position is primarily a platform for promoting President Trump’s handling of the economy, including his tax and trade policies, Ms. Crowley’s appointment is almost certain to raise questions.

She was considered for a high-ranking National Security Council job in 2017 and was also mentioned as a candidate to become the White House press secretary. But she dropped out of contention after the emergence of allegations that she plagiarized key passages in her 2012 book, “What the (Bleep) Just Happened?,” from Wikipedia and newspaper articles.