The statement is mostly true. While there were dissenting opinions, the majority in the North supported Lincoln's decision to make the war a fight against slavery. The move strengthened the Union's cause and conformed to the Northern ideals of liberty and equality.
The statement that Lincoln's decision to make the war a fight against slavery was widely popular in the North can be largely viewed as true. While there were definitely dissenting opinions, the majority in the North supported the Emancipation Proclamation and the essentially moral plan to end slavery. This is because many people in the North believed in the concept of liberty and equality and felt that slavery was against these fundamental principles. Furthermore, Lincoln's decision strengthened the Union cause by preventing any potential European powers from aiding the Confederacy due to their stance on slavery.
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