I recently posted Congressional Enforcement of Affirmative Democracy Through Section 2 of the Voting Rights Act, 25 N. Ill. U. L. Rev. __ (2005) on the SSRN.  Here's the abstract and link:

The constitutionality of Section 2 has been questioned by a number of commentators over the past several years. In this Essay, I argue that even under the Rehnquist Court's precedents, Section 2 is unquestionably constitutional. The Essay first explores a macro-level theory that racial discrimination in voting is "different" both from an equal protection perspective and a congressional enforcement power perspective. This difference will allow for the greater use of race-based remedies to benefit racial minorities when it comes to voting matters and will allow Congress greater latitude to use its enforcement power when it seeks to eradicate racial discrimination in voting. This difference, however, has limits, and these limits are that Congress cannot pass laws that violate separation of powers principles by completely subverting the Court's idea of the substance of constitutional rights and that Congress cannot pass laws that violate federalism principles by overly compromis!
 ing the autonomy of state and local governments. I argue that Section 2 violates neither of these limits.

http://papers.ssrn.com/sol3/papers.cfm?abstract_id=608661