Trump picking Nikki Haley would be the worst decision since Bud Light put that transgender guy on its cans. There are millions of Americans who have Confederate ancestors—they may not want to re-fight the Civil War but they don’t like their ancestors being trashed (and certainly not by a first-generation American with no respect for American history). Trump as a New Yorker may not understand this.
Here's what a lot of people here don't realize. If he earns the nomination, Trump will already have the MAGA vote locked up. Picking a MAGA-friendly VP for the ticket isn't going to win him any new votes.
If he wants to win the General Election, as long a shot as that is, he's going to need to rally the moderates, the small 'c' conservatives, the independents, and the swing voters. He'll pick a VP that will help him with this demographic and these voters don't care about confederate monuments.
Nikki Haley is the obvious choice.