President-elect Donald Trump is starting to fill key posts in his second administration, putting an emphasis so far on aides and allies who were his strongest backers during the 2024 campaign.

Here’s a look at who he’s selected so far.

Susie Wiles, chief of staff

Wiles, 67, was a senior adviser to Trump’s 2024 presidential campaign and its de facto manager.

Wiles has a background in Florida politics. She helped Ron DeSantis win his first race for Florida governor. Six years later, she was key to Trump’s defeat of him in the 2024 Republican primary.

Wiles’ hire was Trump’s first major decision as president-elect and one that could be a defining test of his incoming administration considering her close relationship with the president-elect. Wiles is said to have earned Trump’s trust in part by guiding what was the most disciplined of Trump’s three presidential campaigns.

Wiles was able to help keep Trump on track as few others have, not by criticizing his impulses, but by winning his respect by demonstrating his success after taking her advice.

Mike Waltz, national security adviser

Trump asked Waltz, a retired Army National Guard officer and war veteran, to be his national security adviser, a person familiar with the matter said Monday.

The person spoke on the condition of anonymity to discuss the matter before Trump made a formal announcement.

The move would put Waltz at the forefront of a litany of national security crises, ranging from the ongoing effort to provide weapons to Ukraine and escalating worries about the growing alliance between Russia and North Korea to the persistent attacks in the Middle East by Iran proxies and the push for a cease-fire between Israel and Hamas and Hezbollah.

Waltz is a three-term GOP congressman from east-central Florida. He served multiple tours in Afghanistan and also worked in the Pentagon as a policy adviser when Donald Rumsfeld and Robert Gates were defense chiefs.

He is considered hawkish on China, and called for a U.S. boycott of the 2022 Winter Olympics in Beijing due to its involvement in the origin of COVID-19 and its ongoing mistreatment of the minority Muslim Uighur population.

Tom Homan, ‘border czar’

Homan, 62, has been tasked with Trump’s top priority of carrying out the largest deportation operation in the nation’s history.

Homan, who served under Trump in his first administration leading U.S. Immigration and Customs Enforcement, was widely expected to be offered a position related to the border, an issue Trump made central to his campaign.

Though Homan has insisted such a massive undertaking would be humane, he has long been a loyal supporter of Trump’s policy proposals, suggesting at a July conference in Washington that he would be willing to “run the biggest deportation operation this country’s ever seen.”

Democrats have criticized Homan for his defending Trump’s “zero tolerance” policy on border crossings during his first administration, which led to the separation of thousands of parents and children seeking asylum at the border.

Elise Stefanik, United Nations ambassador

Stefanik is a representative from New York and one of Trump’s staunchest defenders going back to his first impeachment.

Elected to the House in 2014, Stefanik was selected by her GOP House colleagues as House Republican Conference chair in 2021, when former Wyoming Rep. Liz Cheney was removed from the post after publicly criticizing Trump for falsely claiming he won the 2020 election. Stefanik, 40, has served in that role ever since as the third-ranking member of House leadership.

Stefanik’s questioning of university presidents over antisemitism on their campuses helped lead to two of those presidents resigning, further raising her national profile.

If confirmed, she would represent American interests at the U.N. as Trump vows to end the war waged by Russia against Ukraine begun in 2022. He has also called for peace as Israel continues its offensive against Hamas in Gaza and its invasion of Lebanon to target Hezbollah.

Stephen Miller, deputy chief of staff for policy

Miller, an immigration hardliner, was a vocal spokesperson during the presidential campaign for Trump’s priority of mass deportations. The 39-year-old was a senior adviser during Trump’s first administration.

Miller has been a central figure in some of Trump’s policy decisions, notably his move to separate thousands of immigrant families.

Trump argued throughout the campaign that the nation’s economic, national security and social priorities could be met by deporting people who are in the United States illegally. Since Trump left office in 2021, Miller has served as the president of America First Legal, an organization made up of former Trump advisers aimed at challenging the Biden administration, media companies, universities and others over issues such as free speech and national security.

Lee Zeldin, Environmental Protection Agency

Trump has chosen former New York Rep. Lee Zeldin to serve as his pick to lead the Environmental Protection Agency.

Zeldin does not appear to have any experience in environmental issues, but is a longtime supporter of the former president. The 44-year-old former U.S. House member from New York wrote on X, “We will restore US energy dominance, revitalize our auto industry to bring back American jobs, and make the US the global leader of AI.” “We will do so while protecting access to clean air and water,” he added.

During his campaign, Trump often attacked the Biden administration’s promotion of electric vehicles, and incorrectly referring to a tax credit for EV purchases as a government mandate. Trump also often told his audiences during the campaign his administration would “Drill, baby, drill,” referring to his support for expanded petroleum exploration.

In a statement, Trump said Zeldin “will ensure fair and swift deregulatory decisions that will be enacted in a way to unleash the power of American businesses, while at the same time maintaining the highest environmental standards, including the cleanest air and water on the planet.”