WASHINGTON, Sept. 9 — As Labor Day weekend got under way, Senator John W. Warner of Virginia revealed his plan to end his political career, after five terms in the Senate, with a quotation from Thomas Jefferson.

“There is a fullness of time when men should go,” Mr. Warner, an 80-year-old Republican, said in a graceful farewell that recalled the very different departure from the Washington stage of another powerful 80-year-old two years earlier.

Chief Justice William H. Rehnquist died over Labor Day weekend in 2005, 10 months after receiving a diagnosis of an invariably fatal form of thyroid cancer. During most of that time, he had been widely expected to announce a decision to retire, but he kept even most colleagues in the dark about his condition and plans until declaring six weeks before his death that he intended to stay on.

Whether he displayed brave optimism or “a degree of egoistic narcissism,” as Prof. Sanford Levinson of the University of Texas Law School asserted in a recent book, is open to debate. With the protection of life tenure, the decision to play through was, in any event, completely the chief justice’s own.