According to three former senior American officials, Putin sought to kill a double agent in Florida through a clandestine operation.
As President Vladimir V. Putin of Russia has pursued enemies abroad, his intelligence operatives now appear prepared to cross a line that they previously avoided: trying to kill a valuable informant for the U.S. government on American soil.
The clandestine operation, seeking to eliminate a C.I.A. informant in Miami who had been a high-ranking Russian int...
