Here's what I hope is the definitive answer regarding the "contender" quote.
The full quote is:
"I could've been a contender. I could've had class and been somebody. Real class. Instead of a bum, let's face it, which is what I am."
This quote is from the Budd Schulberg screenplay "On the Waterfront" (1954), and was spoken by Marlon Brando. Brando may have spoken the word "could've" as "coulda", in imitation of local speech; I'd need to see the film again to be sure. However, I've seen the line often quoted as "I coulda been a contender".
BTW, it took me literally a minute or so to find the source of the quote and its text (as it appears in the screenplay.) It took longer to type it in.
---Alvin H. Nichter