The term "Manifest Destiny" was coined by Democratic Party political writer John O'Sullivan in a 1845 Democratic Review journal article supporting the annexation of Texas. Those who embraced the idea of Manifest Destiny – initially Democrats, but eventually a significant number of Republicans as well – believed that the United States was destined to build a nation that would reach from the Atlantic to the Pacific. This proposed expansion required encroaching on land that then belonged to Native American tribes, England, Mexico and Spain.

The Opposition Party

Most Whig Party candidates ardently opposed the expansionism proposed in the idea of Manifest Destiny. The Whig Party was a "big tent" party, designed to appeal to a wide variety of voters who were united in their opposition to the policies of Democratic President Andrew Jackson in the 1830s. As such, different Whigs had different reasons for opposing Manifest Destiny and opposed it with varying degrees of fervor.

Reasons for Opposition

Many Whigs opposed annexing Texas, going to war with Mexico and maltreatment of Native Americans simply on moral principles. Others feared that too much expansion would make the still-new practice of self-government too difficult for the young United States. Some Whigs also opposed expansionism because they feared that much of the territory the United States would gain would become open to slavery. Others opposed expansion because of concerns that adding new states would decrease the political power of the states they lived in and represented.