The U.S. Supreme Court takes up yet another incendiary election issue Wednesday when it hears arguments on a controversial Arizona law that targets illegal immigrants. As with last month’s test of the Obama health care overhaul, the case pits the federal government’s assertion of power against some states, and with some exceptions, it pits Democrats against Republicans. The Arizona law before the court, known as SB 1070, has become a model for other states, particularly those dominated by Republicans. Last year, however, a federal appeals court blocked enforcement of key provisions as an unconstitutional encroachment on federal immigration authority. Historically, the federal government has the power to regulate immigration questions, while the states have the power to police illegal activities that threaten health and safety within their own borders. This case pits these two legal concepts against each other.