Final answer:
Union victories, most notably the fall of Atlanta and wins in the Shenandoah Valley, significantly bolstered Lincoln's popularity and aided his reelection in 1864. Lincoln's debates with Stephen Douglas in 1858 showcased his presidential potential, and despite receiving less than 40% of the popular vote, Lincoln's electoral college victory was secured by winning almost all free states.
Step-by-step explanation:
The victories that helped push the election toward Lincoln were due to Union successes in late 1864, particularly the fall of Atlanta to General William Tecumseh Sherman in September, and General Philip Sheridan's triumphs in the Shenandoah Valley of Virginia.
These military achievements significantly boosted Lincoln's popularity, which played a crucial role in his reelection bid. On November 8, 1864, Lincoln won the presidential election with over 400,000 popular votes and an overwhelming electoral majority of 212 to 21 against his opponent, McClellan, who only won three states: Kentucky, Delaware, and New Jersey.
During the 1858 campaign, Lincoln's debates with Stephen Douglas put him in the national spotlight and showcased his strength as a candidate, laying the groundwork for his successful presidential run in 1860. Although Douglas retained his senate seat, the Republican Party performed well in the elections, indicating a shifting political landscape favoring Lincoln.
Despite receiving less than 40% of the popular vote in the presidential election, Lincoln secured a decisive victory in the Electoral College by winning almost all of the free states, with the exception of New Jersey where he split the vote with Douglas. This win was facilitated by a split in the Democratic Party, which guaranteed a Republican victory.