Final answer:
The central idea of the passage is that granting universal suffrage is critical for a truly united nation, which aligns with historical expansions of voting rights in the United States and principles of equal voting power.
Step-by-step explanation:
The central idea of the passage is that granting the right to vote to all is the clearest path to securing a truly united nation. While the passage mentions specific groups who may deserve the right to vote, such as those who have sacrificed for the Union army or individuals who act with intelligence and civility, it culminates with the assertion that universal suffrage is fundamental to unity. This is further supported by historical context and the evolution of voting rights in the United States, indicating a trend towards expanding suffrage.
According to the passage, the right to vote has broader implications beyond just a constitutional right; it is a vital tool for fostering national unity. The passage echoes the principles laid out in the U.S. Constitution and subsequent amendments, which have incrementally removed barriers to voting, including race, color, and previous condition of servitude, as seen in Amendment XV. The Supreme Court has also played a role in equalizing voting power, ensuring one person's vote is worth as much as another's. This foundation of democracy, an educated electorate, and the drive towards inclusivity supports the idea that all citizens should have the right to vote.