President Donald Trump's new White House chief of staff, Stephen Miller, is behind many of the administration's signature domestic policy initiatives - especially its sweeping crackdown on immigration.

An outspoken defender of Trump's most far-reaching goals to remake government going back to his 2016 run for president, Miller is known for his harsh language and unapologetic bombast, attracting outsized attention from supporters and critics alike.

His record is likely to be scrutinized by Democrats in his powerful new role as he leads Trump's White House through a difficult lame duck period after the Republican Party lost both houses of Congress.