What were the political effects of Manifest Destiny in the United States?

Manifest Destiny, the idea that the United States had the divinely-ordained right to expand all the way to the west coast, had a number of political effects. For one thing, it led to the election of several Democratic presidents, notably James K. Polk, who actively promoted it. It led to the annexation of Texas, which led to the Mexican War, itself driven largely by the idea of manifest destiny. The war resulted in the acquisition...

Manifest Destiny, the idea that the United States had the divinely-ordained right to expand all the way to the west coast, had a number of political effects. For one thing, it led to the election of several Democratic presidents, notably James K. Polk, who actively promoted it. It led to the annexation of Texas, which led to the Mexican War, itself driven largely by the idea of manifest destiny. The war resulted in the acquisition of the enormous Mexican Cession, essentially the entire American Southwest, including California. This led to a major indirect political effect of manifest destiny--the political showdown between slave and free states over whether slavery would be allowed in the newly acquired territories. When California applied for admission to the Union, it sparked a major debate over these issues, one which was only momentarily quieted with the Compromise of 1850. Westward expansion was inextricably tied to the ideology of manifest destiny, and it was the persistence of westward expansion that stirred up the lingering issue of slavery. Manifest destiny, or various iterations of it, also contributed to the continued expropriation of Indian lands, which were taken by whites with the assistance of the federal government and the U.S. Army.