President-elect Donald Trump is naming longtime adviser Stephen Miller, an immigration hard-liner, to be the deputy chief of policy in his new administration.Video above: Trump announces cabinet appointments as Republicans eye administration action on immigration, foreign policyConfirming the appointment, Vice President-elect JD Vance posted a message of congratulations on Monday to Miller on X and said, “This is another fantastic pick by the president.” The announcement was first reported by CNN.Miller is one of Trump's longest-serving aides, dating back to his first campaign for the White House. He was a senior adviser in Trump’s first term and has been a central figure in many of his policy decisions, particularly on immigration, including Trump's move to separate thousands of immigrant families as a deterrence program in 2018.Miller has also helped craft many of Trump’s hard-line speeches, and was often the public face of those policies during Trump's first term in office and during his campaigns.Since leaving the White House, Miller has served as the president of America First Legal, an organization of former Trump advisers fashioned as a conservative version of the American Civil Liberties Union, challenging the Biden administration, media companies, universities and others over issues such as freedom of speech and religion and national security.He was also a frequent presence during Trump's campaign this year, traveling aboard his plane and often speaking ahead of Trump during the pre-shows at his rallies.Miller drew large cheers at Trump's rally at Madison Square Garden during the race's final stretch, telling the crowd that, “your salvation is at hand,” after what he cast as "decades of abuse that has been heaped upon the good people of this nation — their jobs looted and stolen from them and shipped to Mexico, Asia and foreign countries. The lives of their loved ones ripped away from them by illegal aliens, criminal gangs and thugs who don’t belong in this country.”“We stand here today at a crossroads,” he went on, casting the election as “a choice between betrayal and renewal, between self-destruction and salvation, between the failure of America or the triumph of America.”Because it is not a Cabinet position, the appointment does not need Senate confirmation.