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. (5-8)
The Mudville fans have attached their sense of hope to their hero, Casey. In the minds of the fans, even against impossible odds, Casey would be capable of saving the day. We expect a lot from our idols and heroes, right? The Mudville fans are no different. They truly believe that Casey can deliver them, their team, and their town from the jaws of defeat.
Then from 5,000 throats and more there rose a lusty yell; […] For Casey, mighty Casey, was advancing to the bat. (17, 20)
The crowd goes nuts when they get a glimpse of "mighty Casey" coming to the plate. They have supreme confidence in their hero. The description of Casey as "mighty" makes him sound almost god-like: mighty Casey, mighty Zeus. In the mind of many Mudvillers (Mudvillians?) the game is already in the bag. With Casey at the plate, the game is as good as won.
"Fraud!" cried the maddened thousands, and echo answered fraud; But one scornful look from Casey and the audience was awed. (41-42)
Casey has this crowd in the palm of his heroic hand. They admire him so much that they are willing to follow his every command. Even when they are swept up in a frenzy of hatred and rage, Casey is able to calm them down with no more than "scornful look."
The relationship between Casey and the crowd seems almost paternal—Casey is scolding the crowd like they are misbehaving children. The crowd looks up to, is "awed" by, Casey, much like a small child looks up to a parent. One stern look from Casey, and they jump right back in line.