Politics and donating

Until recently, I never truly got why people would donate money to a particular candidate. What does my money matter? I could never donate enough to really make a difference. Don't they have enough? Etc, etc. (Yet I don't feel that way about voting.) I just donated to the Barack Obama campaign fund. Honestly, I'm concerned about the country but I feel there's little I can do. The whole system seems to have screwed itself into the mess we're in. I hope my money helps.