Who is Kamala Harris' 'combative Marxist economist' father, Donald J. Harris?

Vice President Kamala Harris has frequently cited her upbringing and family as she crisscrosses the nation in an effort to rally support for her newly-formed presidential campaign, including touting her father in a rare mention at the DNC. 

"My early memories of our parents together are very joyful ones. A home filled with laughter and music: Aretha, Coltrane and Miles. At the park, my mother would say, ‘Stay close.’ But my father would say, as he smiled, ‘Run, Kamala, run. Don’t be afraid.