With only his law practice to sustain him, but still harboring political ambitions, Lincoln decided to make a bid for the Whig nomination in a Congress race in 1843. Much to his dismay, he failed to garner the necessary support even in his home county, and once again he was forced to wait until the next elections to realize his goal. Later that same year, he was mentioned as a candidate for governor of Illinois, but he had no interest in pursuing the position.
In 1844, Lincoln threw his political energy into the presidential race, campaigning actively for his longtime role model and third-time Whig candidate Henry Clay. Due to the third-party candidacy of former president Martin Van Buren, the Democrats were eventually swept into office on the manifest destiny platform of James K. Polk. As the strongest supporter of the annexation of Texas, Polk was able to carry expansionist Illinois, much to the chagrin of Lincoln.
Two years later, Lincoln successfully secured the Whig nomination for a seat in Congress. During the campaign, the Mexican War broke out, and became a major issue in the race. Lincoln reserved his doubts about the conflict, urging young men to volunteer rather than dissecting Polk's motivations or aims. This conservative strategy proved successful, and despite Illinois's reputation as a Democratic stronghold, Lincoln was swept into office by a sizeable majority.
Due to the progress of the war, the Thirtieth Congress did not convene until December 1847, over a year after Lincoln had been elected. By all accounts, in his single, shortened term in Washington, Lincoln failed to leave a significant mark. The only major legislative proposal he fowarded was a plan to establish the gradual and compensated emancipation of slaves in the District of Columbia, subject to free white approval.
This moderate piece of legislation was ultimately scrapped in draft form, for it displeased the abolitionists as a spineless piece of conservatism, and it infuriated the slaveholders as a radical threat to their own interests. Having lost his chance to diminish the institution of slavery, Lincoln sought to contain it, voting in support of the Wilmot Proviso, which provided that all territory gained from the Mexican War would remain free soil.
Although he had masked his initial objections to the Mexican War, and had approved the appropriation of funding for warfare, Lincoln later took the Whig Party line in condemning President Polk for what was termed an unnecessary and unconstitutional act of aggression. As one of the most vocal proponents of this censure, Lincoln made a speech on the House floor in which he pointed out that the Mexicans had made no hostile acts toward the United States and had been attacked in an area which was rightfully theirs. Most significantly, Lincoln reasoned, Polk had overstepped his executive powers "because the power of levying war is vested in Congress, and not in the President.... No one man should have that power."