Russia's political opposition has been put on notice. The Feb. 27 murder of prominent opposition leader Boris Nemtsov just steps from the Kremlin marks a dramatic escalation of the Russian regime's long-running war on its opponents. Nemtsov, after all, wasn't merely a dissenting politician. He was part of the old system, having served as a deputy prime minister in the government of President Boris Yeltsin in the late 1990s. Beginning in the early 2000s, Nemtsov had moved into the political opposition, emerging as a critic of Yeltsin's successor, Vladimir Putin, and his policies. Even so, his position as a member of Yeltsin's inner circle had given him a degree of immunity from official retribution.