The words Narrative/Saga are often heard in the news.
My question is what the exact definition of the words.
I want to know the nuance. The definition found in the dictionary does not much explain the nuance of the word, used in such context below.

Dictionary description:
Narrative >> describing events
Saga >>a long series of events

Looking at the both definition, there is not much difference between two, but clearly they are used differently depending on the context, how can I pick the right choice based on the context?

Ex.1 Nonetheless, the narrative has taken off, and the ost current polls generally find that Clinton is suffering from a deficit of voters' trust, although Trump's numbers tend to be roughly equal.

This narrative means rather "perception”?

Ex.2 Coming off the heels of the Clooneys’ Hillary Clinton fundraiser in L.A., the barrister also spoke about the saga that is the American presidential election, burning Donald Trump without ever mentioning his name.

Why "saga" is used here, why not "narrative”?

Thank you