Bloomberg Opinion columnist Jonathan Bernstein says that both U.S. political parties need to reverse the trend of nominating old candidates for the Senate. He explains that senators in their 30s and 40s used to be common. No longer — and that’s mostly the responsibility of the parties. It’s not hard to think of senators who have been effective at advanced ages, of course. But overall, Bernstein argues, the rising age of the members is related to the overall decline of the Senate.