The term of office for a U.S. Senator is six years. Elections are held every two years to replace approximately one-third of the 100 sitting senators. As of 2014, there are no term limits for senators.
In 1913, three-quarters of the states ratified the 17th Amendment to the United States Constitution. This amendment made it possible for the people to vote for senators instead of the state legislatures electing them. This was seen as a victory for the people. Back then, it was believed that most senators served the interests of powerful people instead of the people they were chosen to represent.