AN EASY ASSUMPTION THAT the eastward expansion of the North Atlantic Treaty Organization (NATO) worries only the foreign policy elite in Moscow has been a characteristic of Western explanations of Russia's response to enlargement since 1996. This view, often supported by references to public opinion polls showing that Russians are more concerned about economic and social issues, is dangerously misleading. Russia's signature on the NATO-Russian Federation Founding Act on Mutual Relations, Cooperation and Security of 27 May 1997, and official acquiescence in the formal invitations offered to prospective new NATO members at Madrid two months later, seem to have lulled Western leaders into …