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.

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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

Daniel Akaka faces Republican pilot John Carroll.

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