What was an advantage of Jimmy Carter in the 1976 presidential election?

He was an outsider.

In 1976, the USA was still reeling from the Watergate scandal which brought down Nixon. His successor Ford was also tarred by the corruption of the Washington system, (he had pardoned Nixon). People were fed up with the political system and Carter an outsider from the South provided an alternative. Four years later it was also to be his downfall.