Thomas Jefferson, Letter to Edmund Pendleton, 26 Aug. 1776, I.2.7

Jefferson would like the senate to be wise and independent. Its members should be elected by representatives of the people since this will greatly increase the likelihood of their being wise (the people being less likely, and their selections more, to elect wise men.) The senators should also be limited to one term (of nine years) since this will let them be free from worry about re-election and therefore independent.