Drop the second major if you're sure you want to do law. GPA and LSAT are 90% of the process. Everything else is marginal at best (unless you're URM, in which case numbers don't really matter).
I agree that GPA and LSAT are 90%, so if one major is keeping your GPA down, drop it immediately. Econ is certainly helpful, but if you can't stay above a 3.5 because of it, it's not doing you any good. I majored in English, maintained a 3.9, and got into Harvard Law School. The major doesn't matter. Your GPA is more important.