Right around the time Republicans were passing around memes of Putin, shirtless, riding a horse and compared it with a photoshopped pic of Obama on some beach in Hawaii?
That's when the Russian full-court press was on hunting for Republicans susceptible to their propaganda.
There are many others in the the Republican party. They are "useful idiots" (in Russian terms), meaning they are easily led, easily steered. Its not like they are actual double-agents, more like easily corruptible tools.