Two points:
First, there’s an adage that says, “the best program to prepare you for X graduate program is the one that nets you the best GPA.” With most grad schools, GPA is a huge part of your application. How strong are you in Econ? If you switch to another major, there’s a possibility your GPA will suffer.
Second, if you’re a junior, do you think you’ll be able to graduate “on time” if you switch majors?
As far as what to study, I’ve known people that have studied poli-sci, economics, environmental sciences, etc. I think a lot of time it comes down to what kind of law they saw themselves wanting to practice.