The main significance of the Lincoln-Douglas debates was that they brought Abraham Lincoln to prominence in the Republican Party, enabling him to secure the nomination to run for president in 1860. Even though Lincoln lost the election for senator of Illinois to Douglas after the debates, he defeated Douglas in the presidential election two years later, according to About.com.
The Lincoln-Douglas debates were a series of seven debates on various topics scheduled between Aug. 21 and Oct. 15, 1858, in various cities in Illinois. Lincoln was relatively unknown, but Douglas was a two-time incumbent. The debates drew national attention and were widely reprinted in newspapers across the nation.
One of the main topics was the subject of slavery. Douglas argued that it was up to the individual territories to decide whether to allow slavery. Lincoln insisted that the country must be united in its acceptance of or rejection of slavery, and that ultimately slavery was morally wrong, as it violated the principle in the Declaration of Independence that all men are created equal. Douglas declared that many of the founding fathers were slaveholders who felt that people had the right to decide these issues for themselves. Douglas' arguments divided and weakened the Democratic Party. The Republicans received a majority of the popular votes, but they lost the Senate seat.