I have read in many creditable sources that there is no best undergrad major, although there are many suggestions for majors based on basic skills that a law student should have. Ex)english (writing and speaking skills), Econ (problem solving skills) etc.... Interestingly, I have even heard of schools discouraging polysci majors due to a possibility of it being a cliché major, though I have rarely seen this argument. Overall, from what I gather, most law schools prefer a diverse background in undergrad majors, hopefully to create a diverse student body.