Nephi's brother is Mufi Hannemann the 12th Mayor of City and County of Honolulu.
Caldwell served as the acting mayor of Honolulu, Hawaii's capital and largest city, during the tsunami evacuation in the absence of Mayor Mufi Hannemann following the 2010 Chile earthquake.
He ran against three other major contenders: Acting Honolulu Mayor Kirk Caldwell who was appointed Managing Director by Mufi Hannemann and became the Acting Mayor when Hannemann resigned to run for Governor, UH Professor and former Mayoral candidate Panos Prevedouros, and City Councilmember Rod Tam.