As early as 2013, the F.B.I. had concerns about Paul Manafort and his deputy, Rick Gates, regarding their “offshore consulting activities,” and interviewed the pair repeatedly. At the time, Manafort was working for Ukrainian President (and Putin puppet) Viktor Yanukovych, from whom he allegedly received more than $12 million in secret payments.

The bureau also had long been interested in Carter Page, an obscure energy consultant whom it had first interviewed in 2013 in connection to his contacts with Victor Podobnyy, a Russian spy based in New York. Page’s chief distinction was his willingness to recite Kremlin talking points on foreign policy.

Manafort joined the Trump campaign in March 2016. Page was named to Trump’s foreign policy team that same month. So was George Papadopoulos, another nonentity with pro-Russian views. Within two months, Papadopoulos was getting word of Russia’s hacking ops via a Kremlin-connected source, which he passed along to former Australian Foreign Minister Alexander Downer that May. The Australians later related this to the F.B.I.

Retired Gen. Mike Flynn, the future national security adviser, had his own financial ties to Russian companies and organizations that would stand to benefit from the lifting of U.S. sanctions on Russia. Flynn’s sudden advocacy for lifting sanctions was especially odd given that he was previously on record as an anti-Russia hawk.

All of this is independent of Christopher Steele’s notorious Russia dossier. Some pundits on the right are now breathlessly trying to claim that the bureau was spying on Page, and thus the campaign, via an informant before the formal investigation began, as if this is an outrage of the first order.

But the significant question is whether any competent counterintelligence officer would not have seen, in this constellation of facts, serious reason to believe that the Trump campaign was profoundly vulnerable to Russian manipulation, even (or especially) if the candidate himself didn’t know about it. Just imagine if Manafort or Flynn hadn’t had their Russia ties exposed and now occupied positions of trust in the White House. The Kremlin would surely know how to leverage their secrets.