Russian opposition leaders Boris Nemtsov, center, and Garry Kasparov, second left, attend a massive protest against Prime Minister Vladimir Putin’s rule in Moscow, Saturday, Feb. 4, 2012. Tens of thousands of Russians flooded downtown Moscow on Saturday to demand an end to Putin’s rule, casting a strong challenge to his bid to reclaim the presidency in March. Saturday’s crowd appeared to be even bigger than two similar rallies held in December, despite temperatures plunging to minus 20 C (minus 4 F). (AP Photo/Ivan Sekretarev)