Why does Lincoln claim at the end of his speech that the union representative form of the government is being threatened?

At the end of his speech, Lincoln argues that the representative form of government is threatened by the growing division and conflict within the nation, particularly due to the issues of slavery and states' rights. He emphasizes that if the nation cannot resolve these differences peacefully and maintain unity, the very principles of democracy and self-governance could be undermined. Lincoln warns that the failure to uphold the Union would set a dangerous precedent, potentially leading to the collapse of democratic institutions not only in the United States but also inspiring similar threats globally.