The Illinois legislature elected Douglas to the United States Senate in 1847 , and Douglas emerged as a national party leader during the 1850s . Along with Henry Clay , he led the passage of the Compromise of 1850 , which settled some of the territorial issues arising from the Mexican – American War . Douglas was a candidate for president at the 1852 Democratic National Convention , but lost the nomination to Franklin Pierce . Seeking to open the west for expansion , Douglas introduced the Kansas – Nebraska Act in 1854 . Though Douglas had hoped the Kansas – Nebraska Act would ease sectional tensions , it elicited a strong reaction in the North and helped fuel the rise of the anti-slavery Republican Party . Douglas once again sought the presidency in 1856 , but the 1856 Democratic National Convention instead nominated James Buchanan , who went on to win the election . Buchanan and Douglas split over the admission of Kansas as a slave state , as Douglas accused the pro-slavery Kansas legislature of having conducted an unfair election
1856 Democratic National Convention
1856 Democratic National Convention
Stephen A. Douglas