President-elect Donald Trump has named Susie Wiles, the manager of his victorious campaign, as his White House chief of staff, the first woman to hold the influential role.

Wiles is widely credited within and outside Trump’s inner circle for running what was, by far, his most disciplined and well-executed campaign, and was seen as the leading contender for the position. She largely avoided the spotlight, even refusing to take the mic to speak as Trump celebrated his victory early on Wednesday morning.

Wiles’s hire is Trump’s first major decision as president-elect and one that could be a defining test of his incoming administration, as he must quickly build the team that will help run the federal government. Wiles does not bring government experience to the role, but has a close relationship with the president-elect.

She was able to do what few others have been able to: help control Trump’s impulses – not by chiding him or lecturing, but by earning his respect and showing him that he was better off when he followed her advice than flouting it.

“Susie is tough, smart, innovative, and is universally admired and respected. Susie will continue to work tirelessly to Make America Great Again,” Trump said in a statement. “It is a well deserved honor to have Susie as the first-ever female Chief of Staff in United States history. I have no doubt that she will make our country proud.”