MOSCOW — First, Vladimir Putin accused Hillary Rodham Clinton of inciting protests against him at the end of 2011. The next fall, the Russian president threw the U.S. Agency for International Development out of his country. Then he decided civic groups that get U.S. financing must be foreign agents. By the end of last year, Putin decided Americans had become unfit to adopt Russian children. This summer he decided to harbor Edward Snowden, the National Security Agency document leaker, despite strenuous U.S. objections. And ever since the Syrian conflict began, Putin has thwarted President Obama’s attempts to get the United...