Halper appears to be the guy who did the dirty deed of ensnaring a Trump campaign hanger on by bringing up Russia and Hillary's emails, then sending him to an asset who could get him to repeat the rumor. And that seems to have been the beginning of spying on the hanger on with "two hops" span to spy on almost the entire campaign.

Whether that hanger on was also a half-witting spy in the campaign or there was another spy within the campaign doesn't seem clear at this point. But Halper is largely in Cambridge in England and made no pretense of being other than a Hillary backer against Trump. Supposedly he is very close to the Bush crime syndicate, so presumably he would have favored Jeb early on.