Former South Carolina Governor Nikki Haley announced on Tuesday that she is running for president, challenging her one-time boss and former president Donald Trump for the Republican nomination.

Haley, 51, served as the United Nations ambassador under the Trump administration before resigning from the position in 2018. Although previously stating she would not run for president in 2024 if Trump did, Haley is now calling for a “new generation of leadership”.

“Republicans have lost the popular vote in seven out of the last eight presidential elections. That has to change,” Haley said in her campaign announcement video released on Tuesday. “It’s time for a new generation of leadership to rediscover fiscal responsibility, secure our border and strengthen our country, our pride and our purpose.”

Get excited! Time for a new generation.

Let’s do this! 👊 🇺🇸 pic.twitter.com/BD5k4WY1CP

— Nikki Haley (@NikkiHaley) February 14, 2023

Along with Trump, 76, President Joe Biden has said he intends to run for re-election. Biden made history when he was elected as the oldest U.S. president (the commander-in-chief is currently 80 years old).

In 2010 Haley was elected governor of South Carolina and re-elected for a second term, but later left the role when Trump appointed her as the UN ambassador following the 2016 presidential election. As the ambassador to the UN, in 2018 Haley announced fresh sanctions against Russian companies accused of aiding Syria’s chemical weapons programme as well as announced that the U.S. was pulling out of the UN Human Rights Council, claiming the council is a “protector of human rights abusers”.

“Some people look at America and see vulnerability. The socialist left sees an opportunity to rewrite history. China and Russia are on the march,” Haley said in her announcement video. “They all think we can be bullied, kicked out. You should know this about me: I don’t put up with bullies. And when you kick back, it hurts them more if you’re wearing heels.”

Haley is Trump’s first major Republican challenger in the 2024 presidential race to date. While the two share many policy agreements, such as opposing abortion and cracking down on illegal immigration, the former governor has criticised Trump on a number of occasions, notably after the January 6th, 2021 capitol insurrection – an attempt to overthrow the results of the 2020 election that named Joe Biden the 46th president of the United States. Trump has been under federal investigation for his role in the events of that day.

After January 6th, Haley said Trump's actions “will be judged harshly by history”. However, she later walked back criticism of the former president, telling Fox News in an interview that “we should not want to go back to the Republican Party before Trump.”

Distinguishing herself as a candidate, Haley is vying to become the first U.S. woman president, as well as the first of Indian descent. As governor, one of her notable actions came in 2015 when she signed a bill that ordered the removal of the Confederate flag – widely seen as a symbol of American slavery – from statehouse grounds, following the murder of nine black churchgoers by a white supremacist.

Other Republicans that are expected to run in the 2024 presidential race include Florida Governor Ron DeSantis, South Carolina Senator Tim Scott and Trump’s former Vice President Mike Pence.