President Trump has chosen Heather Nauert to succeed Nikki Haley as the next U.S. Ambassador to the United Nations. After a rash of criticism from the Left, it's important to recognize that Nauert appears to an objective observer to be very much up to the challenge, just as Haley was. Nauert has been the spokeswoman for the State Department since early 2017. 
Claudia Rosett, IWF's Senior foreign policy expert and veteran foreign affairs reporter, had this to say about Haley and Nauert: 
"Ambassador Nikki Haley has set a terrific example of the importance of prioritizing decency, moral clarity and American interests over the claptrap and bigotries that too often prevail at the United Nations. If Heather Nauert is confirmed as ambassador, her great challenge will be to build on Haley’s work, stand up to aggressors such as Security Council permanent members Russia and China, and keep the world on notice that America is still expecting decent behavior, and taking names."
Others have expressed confidence in her abilities as well. 
“Heather Nauert is capable, well-informed, and articulate,” Clifford May, founder and president of the Foundation for Defense Of Democracies, told The Daily Signal
Despite attempts to discredit her, she's clearly well-versed in foreign policy and willing to stand up to those who would wish harm on the United States:

Secretary of State Mike Pompeo has said Nauert has "extensive experience in this administration in foreign policy and in representing the President's goals."
In addition to experience at the State Department, Nauert has decades of experience as a respected journalist.