I had hesitated to breach this subject, as it is a specialty of Misha's, but as he has not rushed in...
This begins to address what Sen. Biden has called a potential "extraordinary circumstance" that should permit a filibuster. Sen. Biden is not a member of the Gang of 14 that introduced this standard and may not be a competent authority.
It is my bet that Alito will openly support Baker v Carr but be more guarded on Reynolds v Sims.
Should states be allowed to have legislative districts apportioned, for instance, by territory, if they wish? The Constitution guarantees republican government in the states, but does it really mandate one-man-one-vote? Many republican governments have thought it advisable to OVERREPRESENT rural districts (Japan), or sections of the country that are the home to minority ethnic groups (UK). Why should it be viewed as impermissible BY IMPLICATION to adopt such measures here (and, pace Misha, against the express example of the US Sentate)?
So long as the overrepresentation is of the WEAK, should this not be seen as a question of policy, rather than principle? While Faction should be feared, should not counterweight-to-concentration be another prudential tool against tyranny?