What event did Lincoln think change his life in the book Taking Sides?

In "Taking Sides," Lincoln believes that the pivotal event that changed his life was his participation in a series of debates against Stephen A. Douglas during the 1858 Illinois Senate race. These debates not only sharpened his political skills and public speaking but also solidified his stance on slavery and its moral implications, ultimately shaping his future as a national leader. Lincoln viewed the debates as a critical moment that propelled him into the national spotlight and set the stage for his presidential aspirations.