There may be some changes if senators die or resign.

On rare occasions a Senator resigned rather than follow instructions.

If senators in other classes die or resign between 2014 and 2016, there may be additional special elections.

Since 1990, several senators reprimanded by the committee either resigned or did not seek re-election.

Throughout the Senate's history, incumbent senators have seldom resigned to accept cabinet posts.

Senators also resigned at a high rate.

If senators in other classes die or resign between 2012 and 2018, there may be additional special elections before or during the 2018 election.

One reason there are so many close races is that 14 senators (8 Democrats and 6 Republicans) are resigning.

Three re-elected senators, all Democrats, resigned following the election, creating vacancies later filled by special elections on February 22, 2011.

Senators may, however, resign their seats prior to that mark, and can lose their position should they fail to attend two consecutive sessions of parliament.