Thanks for the question!

Ernest Lawrence Thayer’s playful poem “Casey at the Bat” tells the story of a baseball game where the Mudville home-team is losing with a score of “four to two” with a single inning left to play. The atmosphere at the ball game is somber as two consecutive players strikeout. A “pall-like” silence falls over the fans attending the game as they realize their hopes of winning have evaporated.

At this point, the fifth and sixth lines read,

A straggling few got up to go in deep despair. The rest
Clung to that hope which springs eternal in the human breast;

The 5000 Mudville fans in attendance are divided into two groups, those who leave their seats and go home in “despair” and those who stay, hoping that some miraculous event will help their team win the game. The Oxford English Dictionary defines straggle as “an irregular group of people.” In the context of this poem, a “straggling few” tells the reader that those leaving the ball-field are small in number; this is not a mass exodus! While Mudville’s situation is dire enough that a few fans sneak away, most remain to watch the outcome.

I hope this helps!