On Tuesday, voters resoundingly rebuked Donald Trump and his brutal mass deportation campaign that sent military tanks and masked agents though residential streets.

But on Friday, the president doubled down. He named Stephen Miller – the architect of the administration’s most aggressive immigration policies – as his chief of staff.

It was never likely that Trump – who rose to political prominence on the promise that he would expel immigrants en masse from the US – would dampen his agenda, even after voters rejected Republican candidates up and down the ballot, near and far from the southern border, in blue and deep-red states.

But the elevation of Miller – a zealous, anti-immigrant crusader who has been by Trump’s side since the president’s first term – is an ominous signal that the deportation machine that Trump has built up over the past two years will be driving ahead at full speed.

Miller more than any single other person is responsible for unleashing a series of violent immigration raids across US cities this year and last, for sending hordes of masked agents in military gear through residential streets to round up undocumented immigrants. He has pushed the administration to all but shut down legal immigration as well. In his previous roles – as a deputy chief of staff and policy adviser – he has stuck close to Trump’s side and stoked the president’s most extreme instincts.

“The elevation of Stephen Miller to White House chief of staff signals a doubling down on the administration’s cruelest impulses,” said Faisal Al-Juburi, the co-chief executive of Raíces, a Texas-based humanitarian aid and immigration services non-profit. “Miller’s promotion guarantees an acceleration of mass deportations and of brute force unleashed within our neighborhoods.”

After immigration agents shot and killed Alex Pretti, a nurse, amid immigration raids in Minneapolis, it was Miller, according to the Wall Street Journal, who raised the idea that Trump could invoke the Insurrection Act to send in military troops.

It was Miller who came up with the legal framework of using the Alien Enemies Act to cast Venezuelan immigrants – including asylum seekers – as foreign terrorists associated with the Tren de Aragua cartel, and using that reasoning to expel them to a Salvadorian megaprison and to strike small Venezuelan boats.

During the first Trump administration, it was Miller who devised the “Muslim ban” restricting travel from Muslim-majority countries. It was he who designed the now-notorious zero tolerance policy of the first Trump administration – which separated more than 5,600 children from their parents and caregivers at the US-Mexico border. More recently, he’s pushed the administration to accelerate the deportation of undocumented children.

Miller, 41, who is himself the descendant of Jewish immigrants to the US and grew up in liberal Santa Monica, California, came to reject his home town, viewing California as a failed state that had been perverted by mass immigration. Eventually, he came to see immigration as a leftwing plot to undermine his vision of a traditional United States.

In more than a decade by Trump’s side, Miller has worked with the president to wrest extreme executive authority, to undermine Congress and the judiciary and defy oversight – in large part to advance his anti-immigrant campaign.

“He never backs down,” said Trump’s defense secretary Pete Hegseth in a congratulatory social media post, calling Miller a true patriot.

Democratic lawmakers who’ve re-taken control of Congress, governor’s offices and statehouses may have to spend much of the next two years bringing Miller’s ambitions to heel. Human rights activists and advocates on behalf of immigrants are immediately calling on congressmembers to do everything they can to stop Miller.

US representative Robert Garcia, the California Democrat who is poised to lead the House oversight committee next year, warned that Miller “should lawyer up” – promising to investigate him and his involvement in the administration’s mass deportation scheme.

Senator Alex Padilla said that if Trump was doubling down, “so will we”, promising to use “every tool at our disposal – oversight, investigations, subpoenas, and our leverage over federal funding – to expose this administration’s abuse of power and hold those responsible accountable”.

But even with full control of Congress, Democrats will likely have a limited ability to rein in the administration’s immigration enforcement agencies – which are bloated with $70bn in funding through 2029. Immigration and Customs Enforcement is poised to massively expand its workforce. Immigration arrests and detentions are already at an all-time high.

Miller, meanwhile, has shown a unique unwillingness to concede – in 2018, he reportedly sank a deal that would have gotten Trump $25bn funding for a border wall in exchange for a provision that would have provided permanent protection for undocumented immigrants who had come to the US as children.

It hasn’t seemed to faze him that the administration’s policies have alienated the coalition of voters who elected Trump into office in 2024 – including a large contingency of Latino voters. And he is unlikely to be moved by voters’ backlash against the Trump administration’s most extreme policies.

“This puts him in a position of greater power to wreak havoc,” Al-Juburi said.