It's the ultimate question when journalists focus on campaign cash and elected officials' behavior: Can you prove that the money directly influences votes on particular bills?
Ultimately, no, unless officials are caught asking for money in exchange for votes. But short of that, we recently used a regression analysis to show campaign contributions are often a strong predictor not only of aggregate behavior, but of individual votes on individual bills.
The analysis, which focused on 10 major bills from California's 1993-94 legislative session, showed that the more money individual lawmakers took from interests pushing a par-