Nikki Haley could replace Mike Pence as Trump's VP.

Haley has written a book expressing her support for President Trump.

Reports indicate Trump could benefit from Haley as VP.

Some political commentators think Nikki Haley is vying to be President Trump's pick for Vice President in 2020.

The speculation surrounding the former U.S. Ambassador to the United Nations comes in the wake of her new book, "All Due Respect," which hits bookshelves Tuesday.

In the book, which was obtained early from the Washington Post, Haley doubles down on her support for Trump. She also claims to have resisted pressure from then-chief of staff John Kelly and then-Secretary of State Rex Tillerson to undermine President Trump.