Here's a look at her policy positions and how they differ from Trump's.
abortion
As a South Carolina representative and later governor, Haley supported restrictive abortion measures, including a 24-hour “thinking period” for women considering an abortion, and also supported, but failed to eliminate abortion coverage for rape and incest victims in the state's health insurance program.
But during the presidential campaign, she positioned herself as a rational Republican, arguing that the party needed a “consensus” before pushing for a national anti-abortion policy.
She also says birth control should remain legal and women should not be jailed or executed for having an abortion — a stance aimed at endearing her to independents at a time when Democrats are committed to protecting abortion rights.
President Trump is a staunch anti-abortion advocate and has touted the Supreme Court's strikedown of the constitutional right to abortion as a major achievement.
Race
The daughter of Indian immigrant parents and whose middle name means “little one” in Punjabi, Nimalata Nikki Haley has a complicated relationship with race.
In her 2012 memoir, Haley detailed the racism she and her family faced while growing up in the rural South, where her father's Sikh turban was visible and the Randhawas had to buy a house because no one would rent it to them.
As governor, she supported flying the Confederate flag on state buildings but reversed course after mass shootings at black churches.
Her recent comments that the United States has “never been a racist nation” and that the Civil War was fought over states' rights, not slavery, have sparked widespread outrage.
climate
Unlike Trump, who has branded climate change a “hoax”, Haley acknowledges the reality of man-made climate change.
Beyond rhetoric, there is little difference between the two.
As Trump's ambassador to the United Nations, she helped pull the U.S. out of the landmark Paris climate accord, and her proposed tax reform plan includes eliminating hundreds of billions of dollars in green energy subsidies under President Joe Biden's signature climate change law, which she calls a “communist manifesto.”
She also promised to accelerate fossil fuel drilling and weaken the Environmental Protection Agency.
Immigration, LGBT rights, and the economy
She has echoed President Trump, calling for the US to “close” the southern border and stop funding for “sanctuary cities.”
She has sparked controversy by proposing to send troops into Mexico to crack down on drug cartels.
On social issues, he said Florida's infamous education law that bans classroom discussion of sexual orientation and gender identity until the third grade “doesn't go far enough,” and argued the ban should extend to the entire elementary school system.
She has proposed raising the retirement age for younger workers while preserving retirement benefits and government-subsidized health care for those nearing retirement — a move that was until recently standard conservative policy but has drawn criticism from President Donald Trump, whose populist politics have upended the old left-right divide.
Foreign Policy
As Trump's ambassador to the United Nations, Haley made supporting Israel a key issue for her, blocking the appointment of a Palestinian envoy and helping to nullify a UN report that condemned Israel as “apartheid.”
She recently said Palestinians should be deported from Gaza to “pro-Hamas” countries.
Trump has frequently praised Russian President Vladimir Putin and has claimed he could end fighting in Ukraine, which Russia invaded two years ago, in “24 hours” but has not explained how.
While President Trump is an isolationist who believes US allies are “scamming” Washington, Haley supports US military aid to Kiev, characterizing it as support for democracy but also as part of a broader US national security plan.
January 6th
Perhaps the clearest difference between Trump and Haley is their stance on the attack on the Capitol on January 6, 2021. While Haley acknowledged that Biden won the 2020 election, she called the attack a “terrible day.”
At the same time, she has suggested she would support Trump if he wins the party's nomination, even if he were convicted of a felony.