One consideration for the White House: Haley, a former South Carolina governor with her eyes undeniably set on high office some day, was arguably the most high-profile woman in a Trump Cabinet with few women.
Haley, who is viewed as more accepting of the US as a global leader than her increasingly nationalist boss, had largely eclipsed Rex Tillerson, Trump's first secretary of state, in the public eye.
Tillerson also left the administration abruptly, albeit after more public disputes with Trump. His replacement, current Secretary of State Mike Pompeo, has been a more forceful secretary and taken up some of the oxygen previously dedicated to Haley in the foreign policy sphere.
There are 23 Cabinet members listed on the White House website. Elevating Haley, as Ambassador to the UN, to Cabinet status broke with the tradition of previous Republican presidents.
John Bolton, for instance, was US Ambassador to the UN under former President George W. Bush and was not a member of the Cabinet. Bolton is now Trump's National Security Adviser and has reportedly disagreed with Haley on key issues.
With Haley, there were six women in Trump's Cabinet -- 26%, a lower percentage than Barack Obama's Cabinet, which ranged between 30% and 35%, but higher than George W. Bush, whose Cabinet had between 19% and 24%, according to data compiled by the Center for American Women in Politics at Rutgers
. If it is not a woman who replaces Haley, the percentage of women in Trump's Cabinet would fall to 22%.
Here's the full list of Cabinet heads, according to the White House:
- Administrator of the Small Business Administration Linda E. McMahon
- Director of the Central Intelligence Agency Gina Haspel
- Secretary of Education Elisabeth Prince DeVos
- Secretary of Transportation Elaine L. Chao
Representative of the United States to the United Nations Nikki R. Haley
- Secretary of Homeland Security Kirstjen Nielsen
- Attorney General Jeff Sessions
- Director of National Intelligence Daniel Coats
- Director of the Office of Management and Budget Mick Mulvaney
- Secretary of Agriculture Sonny Perdue
- Secretary of Commerce Wilbur L. Ross, Jr.
- Secretary of Defense James Mattis
- Secretary of Energy James Richard Perry
- Secretary of Health and Human Services Alex Azar
- Secretary of Housing and Urban Development Benjamin S. Carson, Sr.
- Secretary of the Interior Ryan Zinke
- Secretary of Labor Alexander Acosta
- Secretary of State Mike Pompeo
- Secretary of the Treasury Steven T. Mnuchin
- Secretary of Veterans Affairs Robert Wilkie
- U.S. Trade Representative Robert Lighthizer
- Vice President Michael R. Pence
- White House Chief of Staff John F. Kelly
How women are treated and represented in US government is a key issue in the midterm elections next month. Democrats have made elevating women to Congress a key part of their platform and more women are running for elected office than ever before.
The political drama surrounding Christine Blasey Ford's accusation that Supreme Court Justice Brett Kavanaugh sexually assaulted her when the two were in high school has further focused the election on gender issues. Kavanaugh has touted that he will have only women law clerks for his first term on the bench -- a Supreme Court first.
Haley, for her part, said at the White House Tuesday that she'll be supporting President Trump and Republicans in coming elections.