President-elect Donald Trump made good on one of his campaign promises Tuesday night when he officially appointed billionaire Elon Musk to lead the new “Department of Government Efficiency,” along with entrepreneur Vivek Ramaswamy.

Musk has been so aggressive in pushing his views about Trump’s second term that he’s stepping on the toes of Trump’s transition team and may be overstaying his welcome at Mar-a-Lago, according to two people familiar with the transition who have spent time at the Palm Beach, Florida, resort over the past week.

Musk has spent days bounding in and out of meetings, sitting in on phone calls, weighing resumes and traveling to Washington as Trump’s unofficial co-president.