Bill Weld

William Floyd Weld (born July 31, 1945) is an American attorney, businessman and Republican politician. 
He was the 68th Governor of the Commonwealth of Massachusetts from 1991 to 1997. Bill Clinton named him to be Ambassador to Mexico in 1998, but he was not approved by the Senate. He was the Libertarian vice presidential nominee in the 2016 election.
In April 2019, Weld announced his candidacy for President of the United States in a primary challenge against President Donald Trump in the 2020 election.
Failed ambassadorship nomination.
He resigned as governor in 1997 to focus on his nomination by President Bill Clinton for United States Ambassador to Mexico, but because of opposition by the social conservatives such as Senator Jesse Helms, he was denied a hearing and withdrew his nomination.
2016 vice presidential campaign.
In May 2016, former New Mexico Governor and Libertarian presidential candidate Gary Johnson named Weld as his running mate and he became the vice presidential nominee for the 2016 election. They were later both formally nominated at the Libertarian National Convention. 
2020 presidential campaign.
In January 2019, Weld expressed interest in running for President of the United States as a Republican, challenging President Donald Trump in the primaries, in the 2020 election. In February 2019, Weld rejoined the Republican Party. He launched an exploratory committee for a possible 2020 bid.
On April 15, 2019 Weld officially announced he would be running for President, challenging incumbent Donald Trump.