Mike Pence's Presidential Ambitions and Historic Campaign Against Trump.

Former Vice President Mike Pence is making history by running for the Republican nomination against former President Donald J. Trump, the president who originally put him on the ticket. This is the first time a former vice president has directly challenged a onetime running mate in this way. While it is not unusual for tension and even enmity to develop between presidents and vice presidents, vice presidents typically owe their national stature to the presidents who chose them, and even if they are not especially grateful, they rarely find it politically feasible to compete with their patrons.