Stephen Miller takes over as Chief of Staff

(CNN, KYMA) - Stephen Miller officially took over as President Donald Trump's White House Chief of Staff Monday.

The 41-year-old replaces Susie Wiles, who is moving to Trump's political operation.

Miller is one of President Trump's longest-serving and most influential advisers and a key architect of his hard-line immigration policies.

His promotion comes after sweeping Democratic victories in last week's midterm elections.

According to the New York Times, Miller plans to focus on rebuilding the fractured MAGA coalition and advancing policies that will energize Trump's base.

He's also expected to face intense scrutiny from congressional Democrats when they take power next year.

Trump has not explained why he replaced Wiles, but called Miller one of his most trusted advisers.