A straggling few got up to go in deep despair. The rest Clung to that hope which springs eternal in the human breast; They thought if only Casey could but get a whack at that— We'd put up even money now with Casey at the bat.
The crowd's mood doesn't improve as the second stanza begins. In fact, some folks actually get up and leave. But as is always the case, the die-hard fans remain, clinging to that "eternal" hope.
What keeps those fans in their seats is the hope that Casey might get a chance ("a whack") to get to the plate and drive in some runs.
This Casey guy is apparently so good (think Babe Ruth and Barry Bonds rolled into one… er, minus the performance enhancing drugs) that, despite the bleak outlook, these fans would be happy to bet their hard earned cash that he will come through in the clutch.
Now, let's talk about poetic form for a sec—hey, wait. Come back! We will keep it short and sweet. We promise.
You probably noticed some form-y type things happening in these first two stanzas. First off, all the stanzas have four lines.
These orderly little units are known as quatrains.
Next up: rhyme time. You don't have to be a member of the Poetry Society of America to see that this poem is using a strict rhyme scheme. Thayer wasn't trying to be subtle. These rhymes are strong and regular, with an AABB end rhyme pattern.
You may have also noticed a distinct rhythmic quality in these lines.
That's thanks to our poetry pal the iamb. Casey is written in iambic lines.
Put all these form-factors together and we can deduce that this poem is, in fact, a ballad. (Oh, and also it says "ballad" right there in the poem's epigraph.)
If you're just dying to know more about the poem's form, jump ahead to the "Form and Meter" section.