A narrative, as either the principal plot or a background storyline, that introduces and develops a mythic theme. Also: mythological arc, mytharc.
Although Missouri and South Carolina herald [John Kerry's] first encounters with black voters, his standard campaign speech makes no mention of civil rights or positive discrimination. Instead, he is running on his "mythic arc", the term coined by Washington commentators to describe how the candidates plunder their biographies for electoral gain.
Suzanne Goldenberg, "On a roll and looking like a winner, Kerry faces acid test," The Guardian (London, England), January 31, 2004
[Howard Dean] has a problem with his mythic arc. Presidential campaigns trace the patterns of mythological adventure, as contenders strive to show they are superior in the knightly virtues of temperance, loyalty and courage.
Once candidates showed that they had completed the "hero-task" by highlighting their war exploits J.F.K. and PT 109, George Bush senior getting shot down as a young Navy pilot over Chichi Jima.
Candidates in the Vietnam War generation who chose not to go to Vietnam had to find more personal dragons and giants to slay. Bill Clinton told the story of confronting an abusive and alcoholic stepfather; George W. Bush recounted overcoming alcoholism and career drift by embracing Christ.
In Iowa, Mr. Gephardt talks about the transforming experience of his son's battle against cancer. Mr. Kerry describes the crucible of Vietnam. John Edwards's arc is going from the son of a millworker to a Grishamesque trial lawyer standing up against corporate malefactors.
Shunning personal storytelling, Dr. Dean has chosen to make his campaign arc about his campaign arc. He brags of facing down the dragon George W. Bush.
Maureen Dowd, "Dudgeons And Dragons," The New York Times, December 18, 2003
But beneath this archetypal Houston success story, with its clean mythic arc, lurks another business saga: one as richly complicated and tempestuous as a Cajun soap opera.
Alison Cook, "Food fight," Houston Press, June 30 ,1994
Literary critics have long spoke of a work's dramatic arc (1963), while the Hollywood and television cognoscenti have begun more recently to speak of a movie or show having a story arc (1983). The former is more concerned with the work's overall plot development, while the latter usually deals with an underlying theme, especially (in TV) one that is developed over a series of episodes (think: "The X-Files" and "The truth is out there").
The mythic arc is the story arc writ large, usually in the form of the hero journey, which mythologist Joseph Campbell called the monomyth because it is found in all cultures, religions, and spiritual traditions.