Money isn't everything in politics, but it is a great deal.  The side with a big funding advantage will generally win unless the issues or people involved are so well known to the people that a torrent of advertising can't sway them.

Most voters don't know much about the candidates for district attorney in the typical DA race, and that makes a flood of cash from big-money donors especially dangerous.  Paige St. John and Abbie Van Sickle have this article in the L.A. Times regarding the efforts of George Soros and other well-heeled donors to elect soft-on-crime district attorneys.

Update:  David DeBolt has this article in the San Jose Mercury-News on the same topic, focusing on the Bay Area races:  Alameda and Contra Costa Counties.