MANAGUA, Nicaragua — She started out as a teenage mother working as a newspaper secretary, then spent decades of revolution, conflict, power and public scandal at the side of one of the region’s most influential men.

Now the first lady of Nicaragua, Rosario Murillo, has succeeded in doing something that seems more like a plotline out of the Netflix series “House of Cards”: She will be on the Nov. 6 ballot to become vice president.

Her running mate? Her husband, President Daniel Ortega.

The election, in which the couple’s victory and Mr. Ortega’s third consecutive term are all but certain, is a critical step in what people around Ms. Murillo describe as her decades-long climb to power. She paved the way by helping the poor and winning over the public, but also by holding political grudges and pushing aside nearly all the members of her husband’s inner circle.

“Denying something to my mother is a declaration of war,” her daughter Zoilamérica Ortega said.

But in many ways, the first lady’s spot on the presidential ticket is an acknowledgment of the role she already plays in the country.