A new phenomenon is that newly elected members of the Senate are tending to come into office at advanced ages.
In 2019, we could have two new Senators in their 70s upon taking the oath of office to serve their states in the Senate.
Mitt Romney, the former Republican nominee for President in 2012, is almost certain to win the Senate seat in Utah, and he would be two and half months short of 72 in January 2019.
Phil Bredesen, the former Democratic Governor of Tennessee, if he wins the open Senate seat, would be two months past 75 in January 2019.
They would both surpass two other Senators who were a bit younger–Republican S. I Hayakawa of California who took office in 1977 at age 70; and Angus King, Independent of Maine, who was 68 in 2013 when first came to the Senate, and running again now in 2018 at age 74.