"Of" as a Verb Substitute
People often write the way they speak. That is not always a bad thing, but it does sometimes lead to errors such as:
I could of won.
Presumably this mistake occurs because people are accustomed to hearing and saying, I could’ve won, I could’ve helped you, or I should’ve been there. The ve in the contraction is mistakenly transcribed as of.
The correct version is:
I could have won.