Bill Richardson, former New Mexico governor, has died | USA TODAY

Bill Richardson, the former governor of New Mexico and diplomat has died at 75.

RELATED: Kidnapped American aid worker Jeffrey Woodke has been freed from Niger https://tinyurl.com/mwud8vbm

Bill Richardson, the politician and diplomat who came to be one of the most influential negotiators for Americans held hostage abroad, died Friday at age 75.

Though he had been a congressman, a cabinet secretary and a 2008 presidential candidate, he went always by the moniker "the Governor," from his time as governor of his home state of New Mexico.

Yet the governor carved out perhaps his greatest influence later in life, as an international advocate who worked both inside and outside government channels. His role in freeing hostages and other wrongly detained Americans earned him a nickname from President Bill Clinton: "undersecretary for thugs."