Washington — President-elect Donald Trump will nominate New York Rep. Elise Stefanik to serve as U.S. ambassador to the United Nations, tapping a key House ally to join his administration.

Stefanik, 40, has been one of Trump's most vocal defenders in Congress. She's likely to be confirmed by the new, GOP-led Senate when the president-elect takes office in January, which will set up a race not only to fill Stefanik's seat in the lower chamber, but also to succeed her as chair of the Republican conference.

"I am honored to nominate Chairwoman Elise Stefanik to serve in my Cabinet as U.S. Ambassador to the United Nations," Trump said in a statement to CBS News. "Elise is an incredibly strong, tough, and smart America First fighter."

Here is what to know about the New York Republican.

Stefanik's record in Congress

Stefanik was elected to represent New York's 21st Congressional District in 2014 and at the age of 30, became the youngest woman elected to Congress. Currently in her fifth term, she cruised to reelection in November, defeating Democrat Paula Collins with more than 62% of the vote.

Stefanik serves on the Armed Services, Education and Workforce, and Intelligence Committees. She also is a member of the Select Subcommittee on the Weaponization of the Federal Government, which was created in 2023 when Republicans took control of the House. The weaponization panel was a nod to what many Republicans believed was federal investigators' unfair treatment of Trump.

The New York Republican is the highest-ranking woman in the House, serving in leadership as the GOP conference chair. She replaced former Rep. Liz Cheney of Wyoming in the post after Cheney was ousted for her criticisms of Trump following the Jan. 6, 2021, assault on the U.S. Capitol.

Stefanik has been one of Trump's staunchest defenders in the House, having emerged as a crucial ally during his first impeachment proceedings in 2019. She also introduced a nonbinding resolution last year that sought to "expunge" both of Trump's impeachments by the House.

During this Congress, Stefanik made headlines for her grilling of university presidents during a hearing about their response to antisemitic incidents following the Oct. 7, 2023, terror attacks on Israel by Hamas. The presidents of Harvard, Stefanik's alma mater, and the University of Pennsylvania resigned following the hearing.

While Stefanik supported earlier packages sending assistance to Ukraine, she voted against a plan to send $60.8 billion to aid Ukraine in its war against Russia in April.

Stefanik and the 2020 election

The congresswoman was among a group of more than 100 House Republicans who signed onto a friend-of-the-court brief filed with the Supreme Court after the 2020 election in a longshot bid to overturn the election results in four battleground states. She also joined GOP lawmakers in objecting to certifying Pennsylvania's election results.

"Tens of millions of Americans are concerned that the 2020 election featured unconstitutional overreach by unelected officials and judges, ignoring state election laws," Stefanik said during a speech on the House floor after the Capitol attack. "We can and we should peacefully discuss these concerns."

But the congresswoman also condemned the violence of Jan. 6 during the same speech, calling it a "truly tragic day" for the country.

"We all join together in fully condemning the dangerous violence and destruction that occurred today in our nation's Capitol," she said. "Americans will always have the freedom of speech and the Constitutional right to protest, but violence in any form is absolutely unacceptable, it is anti-American, and must be prosecuted to the fullest extent of the law."

Earlier this year, Stefanik would not commit to certifying the results of the election, telling NBC News in January it would depend on whether "this is a legal and valid election."

Stefanik before Congress

Stefanik graduated from Harvard University and worked in the White House for President George W. Bush on the Domestic Policy Council and in the chief of staff's office. She also was an adviser to former House Speaker Paul Ryan during the 2012 presidential campaign, when he was the Republican vice presidential nominee.

Stefanik and her husband, Matt, have one son, Sam.