The political environment in the 1850s was exceptionally tense because of the debate over slavery. Lincoln represented a new party, the Republicans, who believed in "free soil" for western territories, meaning the containment of slavery within the South. Democrats were divided over the question, but Douglas believed that westerners should decide for themselves whether or not to allow slavery.
By rigidly supporting "popular sovereignty" in the western territories, Senator Douglas found himself at odds with leaders of his own party. In late 1857, President James Buchanan endorsed a proslavery constitution for Kansas, but Douglas refused to go along. This rupture between leading Democrats shocked the nation's political community.
Opposed by a president from his own party, Douglas began the year in 1858 uncertain about his upcoming reelection. Some Republicans saw this as a great opportunity. Horace Greeley, a leading Republican newspaper editor, openly talked about the possibility of accepting Douglas into the Republican Party. But Abraham Lincoln objected.
On June 16, 1858, the Republican convention, meeting at the State House in Springfield, endorsed former congressman Lincoln as their "first and only choice" for U.S. Senate.
Lincoln responded to his party's endorsement with a startling prediction. "A house divided against itself cannot stand," he warned regarding the nation's division over slavery.
"I shall have my hands full," Douglas said after learning that Lincoln had been nominated to face him. He discovered how full only after returning to Illinois and finding that Lincoln planned to follow him around the state. Lincoln was even suggesting as many as 50 debates. Annoyed but unintimidated, Douglas agreed to what he called seven "joint discussions."
The first debate occurred in Ottawa on August 21. The town’s population literally doubled overnight as more than 10,000 people arrived to hear the candidates. Banners were everywhere. The diverse crowd strained to hear the open-air debate. Newspapers paid shorthand reporters to take down every word and wired reports across the country.
After the first debate, Lincoln admitted, "The fire flew some." Douglas had been on the attack, accusing his opponent of various sins, especially for being too radical on the slavery question, a charge that Lincoln struggled to deny. A week later in Freeport, Lincoln appeared stronger, putting Douglas on the defensive with questions about his views on slavery.
By the Jonesboro encounter in mid-September, a pattern was clear. Even though Illinois had no slaves, the 1858 debates focused exclusively on the fate of slavery. Douglas argued that white people should decide for themselves whether or not to allow it, while Lincoln claimed slavery was immoral and should eventually be abolished.
The challenge for Lincoln was to explain what would happen after slavery was extinguished. Douglas knew most whites feared this prospect and pressed Lincoln repeatedly, even making sneering references to Frederick Douglass, the famed abolitionist and former slave. At Charleston, Lincoln conceded that he was not yet ready to commit to full political or social equality.
The Quincy debate witnessed Lincoln at his most aggressive, accusing Douglas of ducking, and lying, and even of “forgery” in his use of documents. The senator responded by claiming his opponent had indulged in “gross personalities” and “false” charges. It was mid-October and the close contest had reached its nastiest point.
Douglas led off the final debate by highlighting his independence and claiming that Lincoln’s House Divided doctrine was a "slander upon the immortal framers of our constitution." He predicted national destruction if the Republicans prevailed. Lincoln replied by arguing that the real "issue" of the contest was "the eternal struggle" between "right and wrong."
Nobody knows for sure what impact the great debates had on the 1858 Illinois elections. Republicans won the majority of popular votes in the legislative contests, but since not all legislators were up for election and because the apportionment of seats was imperfect, Democrats retained control of the General Assembly and succeeded in reelecting Douglas.
Lincoln's optimism after the 1858 campaign soon appeared justified. Despite losing the election to Douglas, the Springfield attorney was invited in 1859 to give campaign speeches in five different northern states or territories and received what Lincoln called his "highest compliment" -- a request to publish the text of the debates by political friends in Ohio.
Lincoln and Douglas faced each other again in 1860 as presidential candidates, though in this contest they had no debates and were joined by two other contenders, John Breckinridge and John Bell. The result was another close election, but this time with a much different result. Lincoln and the Republicans prevailed, secession began, and the nation lurched toward war.