Final answer:
Zachary Taylor was a military leader and 12th President of the U.S., who was selected to lead in the Mexican-American War due to his skills and emerged as a hero, subsequently leading to his presidential nomination by the Whig Party.
Step-by-step explanation:
Zachary Taylor was a key military leader during the Mexican-American War and later became the 12th President of the United States. Selected by President Polk, Taylor was given the task of approaching the Mexicans due to the strategic U.S. military objectives during the war. His initial goal was to take control of northern Mexico, including New Mexico. With superior weapons, Taylor and his Army of the Center captured Monterrey and he emerged as a war hero, greatly admired by the American public. Consequently, President Polk appointed him as commander of all U.S. forces, elevating his military and public stature.
The Whig Party later nominated Taylor for the presidency. They chose him due to his war hero status combined with his image as 'Old Rough and Ready' which appealed to the average voter. Taylor also owned plantations in Louisiana and Mississippi, assuring that southern Whigs would remain loyal. Historian James M. McPherson points out his nomination underscored the complexity of American politics at the time.
During the war, Polk had pushed Taylor into disputed territory to provoke Mexico, leading to the breakout of hostilities and an eventual declaration of war by the United States. This move played a significant role in propelling Taylor to the forefront of national politics and ultimately the presidency after the war, following the signing of the Treaty of Guadalupe Hidalgo and dealing with the Mexican Cession.