Lincoln strengthened the country even though at times it was divided. Lincoln listened to the people and had helped them to make decisions regarding the nation. Democracy is having the people vote and make decisions about the country. Since slaves were not given the freedom to make any decisions, winning the war would allow them to do so.
This is how Lincoln strengthened democracy in the United States. Even though Confederates did not agree with Lincoln, they were experiencing democracy by getting to make decisions for themselves. However, sometimes it takes one side to make rules in order for the other side to understand their place in the democracy. Lincoln strengthened democracy in the United States by the choices he made with the citizens in the United States.