Sounds like he was elected in a political vacuum and became popular enough to remain in office, his reputation growing with each campaign and the telling of his story.
Lyndon B. Johnson loved to wave his Silver Star around on the soapbox.
Some wag described his decoration as "The least deserved, but most appreciated medal ever awarded."
Believe he earned the star by flying as a passenger in a cargo plane in the Pacific theater, but sure he made up with rhetoric, as a US Rep at the time, in the citation what he lacked in valor.
Kerry, same thing. He made his service an issue, like Sheehan waved her brave son's bloody shirt. It's an issue because he opened the door, not his critics.