Boris Yeltsin has an exquisite sense of timing. Just when Mikhail Gorbachev had soundly defeated hard-line rival Yegor Ligachev and secured his control over the divided Communist Party, Yeltsin threw down an even greater challenge. He quit the party, threatening to wrest the embattled reform movement from Gorbachev's hands and turn the party into a sideshow.
For the five years Gorbachev has been in power, his every move has been dogged by these two men, shadow members of a strange political troika. Ligachev was the archconservative, unwilling to sacrifice ideological certainties for the risks of change; Boris Yeltsin, the maverick populist,...