In the early years of the Republic, the system of indirect election of senators seemed to work well. After several decades, however, growing partisanship in some state legislatures resulted in contentious deadlocks that created vacant Senate seats. By the latter half of the 19th century, the system began to break down as intimidation and corruption marked some of the states' selection of senators.
Despite the frequent vacancies, disputed election results, and the growing number of calls for reform, the Senate itself resisted change, forcing states to initiate reforms on their own. Oregon pioneered direct election and experimented with different measures over several years until it succeeded in 1907. Under the so-called "Oregon Model," candidates for the state legislature pledged to support the Senate candidate who won the popular vote in a primary election. Such experiments laid the foundation of other states to adopt measures reflecting the people's will. By 1911 more than half the states were utilizing some element of popular election in the selection of senators. As more senators came to the Senate through these new state-instituted measures, support for a constitutional amendment grew. On June 12, 1911, the Senate finally agreed to the proposed constitutional amendment.