We elect a U.S. Senator for how many years?

Why this is the answer

A U.S. senator serves a six-year term. The people who wrote the Constitution chose that length on purpose. They wanted senators to have some distance from the mood of the moment, and a fairly long term was the protection they settled on. It also offsets the House, whose members face the voters every two years and are expected to track public opinion closely. The Constitution added a second safeguard. It divided the senators as evenly as possible into three classes so that one third would be chosen every second year. That rotation is why only about a third of the Senate is on the ballot in any election year, which always falls on an even-numbered year, and why the chamber is never replaced all at once. The other two thirds stay in their seats. How senators get the job has changed, though the length of the term has not. Under the original text, each state legislature picked its two senators. The 17th Amendment, ratified in 1913, handed that choice to the voters of each state and kept the six years. A senator must be at least 30 years old, have been a U.S. citizen for nine years, and live in the state he or she represents. The Constitution sets no limit on how many terms a senator may serve. Federalist No. 63 gives a sense of what the framers expected from a slower chamber. It described the Senate as a possible defense of the people against their own temporary errors and delusions, so that the cool and deliberate sense of the community could prevail. What trips people up here is swapping numbers between offices. Two years is a representative, four is the President, six is a senator. One way to keep the Senate straight is that its term equals three House terms, the same number as the classes that rotate through it.