Final answer:
Abraham Lincoln, as an Illinois representative, was critical of the Mexican-American War and opposed the annexation of Texas and the expansion of slavery into new territories acquired from Mexico.
Step-by-step explanation:
Abraham Lincoln's Position on the Mexican-American War
During his time as an Illinois representative, Abraham Lincoln was a critic of the Mexican-American War. He challenged President James K. Polk's actions by issuing the "Spot Resolutions," demanding to know the exact location where Americans were fired upon, suggesting Polk had instigated the war to annex slave territory. Although his Whig party was largely sidelined during the war, Lincoln's opposition was clear, and he was skeptical about the expansion of slavery into territories that the United States acquired from Mexico. Consequently, Lincoln did not support the immediate war against Mexico, nor did he support the annexation of Texas due to the implications it could have on the expansion of slavery.
After the Treaty of Guadalupe Hidalgo, the issue of slavery in the territories gained from Mexico became a contentious topic. Both John C. Calhoun and Lincoln understood that this would bring slavery back into national political discussions, intensifying sectional divides that would contribute to the run-up to the Civil War. Ralph Waldo Emerson articulated a similar concern, predicting that the annexation of Mexican territories would bring dire consequences to American politics.