From a certain perspective, certainly the Kremlin’s, Vladimir Kara-Murza’s behavior in Washington could be seen as treasonous, a brazen betrayal of his homeland.

In a series of public meetings on Capitol Hill, Mr. Kara-Murza, a leader in the Russian opposition, urged American lawmakers to expand economic sanctions against the Russian government under a law known as the Magnitsky Act. That would hasten political change in Russia, he argued.

Back in Moscow a month later, in May 2015, the changes Mr. Kara-Murza detected were going on in his own body. Midway through a meeting with fellow dissidents, beads of sweat inexplicably dotted his forehead. His stomach churned.

“It all went so fast,” he recalled. “In the space of about 20 minutes, I went from feeling completely normal to having a rapid heart rate, really high blood pressure, to sweating and vomiting all over the place, and then I lost consciousness.” He had ingested a poison, doctors told him after he emerged from a weeklong coma, though they could find no identifiable trace of it.

While Mr. Kara-Murza survived, few others in his position have proved as lucky. He said he was certain he had been the target of a security service poisoning. Used extensively in the Soviet era, political murders are again playing a prominent role in the Kremlin’s foreign policy, the most brutal instrument in an expanding repertoire of intimidation tactics intended to silence or otherwise intimidate critics at home and abroad. Continue reading.