Daniel Akaka of Hawaii and Keith Roark of Idaho all endorsed Obama Monday, giving him a lead of four superdelegates for the time being.

CNN: Obama takes superdelegate lead on eve of expected loss

One in 5 U.S. senators is 70 or older, and some have retired rather than seek new terms, such as Hawaii's Daniel Akaka, who left office in January at age 88.

NPR: Pope Shows Lifetime Jobs Aren't Always For Life

Daniel Akaka won the Democratic primary Saturday by a margin of 54 percent to 45 percent despite tough opposition from Rep. Ed Case, the cousin of America Online founder Steve Case.

CNN: Akaka wins Hawaii primary