What does "fight the good fight" mean?

Factual Questions
1

What is the vernacular meaning of “fight the good fight”?

I’ve Googled and found that it’s a snippet of a Bible quote, and at least one Christian group is selling T-shirts & merchandise with this slogan.

However, I’ve heard it used several times without a distinct Christian tie-in. One specific example would be the lyrics to the Lucy Kaplansky tune My Name Joe (Google on: lucy kaplansky my name joe lyrics).

So… what’s the meaning of “fight the good fight”? Or “that person fights the good fight”? Is it a distinctly religious reference? Does it mean “standing up for what is right”? (For example: did the Allies “fight the good fight” against Hitler?)

Thanks.

2

My understanding has always been that it means roughly the same thing as “run to win”; that is, to make a sincere and valid effort, to try hard. There is the added connotation that the sustained and strenuous effort one is making is on behalf of a just cause.

3

Yeah, that’s always what I figured. Fight the fight that is for a good cause.

4

It means fight for what you believe in.