While the correspondence between Trump Jr. and WikiLeaks was often one-sided—with the president’s son responding to some messages, but not others—what matters is that the campaign was sufficiently responsive to send Assange an unambiguous message: His support was welcome. When the group told Trump Jr. that it had identified the hosts of an anti-Trump website, the president’s son responded that he’d “ask around [the campaign]” for more information about the individuals involved. “Thanks,” he added appreciatively. Message sent—and doubtless received.

The president’s son’s direct and collaborative engagement with WikiLeaks reflected the campaign’s judgment that the Assange organization was a political ally. And what Trump Jr. did not say also spoke volumes about the nature of this relationship: At no point in the messages obtained by The Atlantic did he advise WikiLeaks that the campaign could not and would not engage with a foreign organization widely understood to be trafficking in illegally obtained materials on behalf of a foreign government. There is no indication on public record to date, nor has the Trump campaign so far claimed, that any of the senior campaign officials aware of the contact with WikiLeaks communicated that message.

The Trump campaign’s actions seem to raise, rather clearly, a violation of the federal prohibition on knowingly providing “substantial assistance” to a foreign national’s campaign expenditures. There is no question that WikiLeaks and the Russians were engaged in campaign spending: The resources used in the hacking and public dissemination of the emails constitute expenditures by foreign nationals. Nor is there doubt about the substantiality of the campaign’s assistance. Both the president and Trump Jr. promoted to the American public the fruits of Russian hacking, shortly after WikiLeaks’ specific request to do so. The president tweeted his belief in the email trove’s significance, as did Trump Jr. The president’s son furthermore tweeted the link specifically provided by WikiLeaks.

WikiLeaks and Russia would also have benefited from the knowledge, conveyed by Trump Jr. and Sr.’s responsiveness, that their activities were consistent with the campaign’s strategic goals. They need not have doubted whether the campaign valued their efforts. They maintained direct contact with the Trump campaign that would have confirmed that, from the campaign’s point of view, these foreign national activities were a genuine asset to the Republican nominee.

This reassurance qualifies as substantial assistance to foreign national spending. Campaign-finance rules can seem obscure, but in this instance, they seem to apply with crystal clarity. The law on aiding and abetting brings the point out in plain terms: As the fabled jurist Learned Hand once put it, the aider and abettor is one who “associate[s] himself with the [illegal] venture, … participate[s] in it as in something that he wishes to bring about, [and] seek[s] by his action to make it succeed.” This seems to capture precisely the Trump campaign’s 2016 engagement with the WikiLeaks-Russian political partnership.

Trump Jr. dismissed his private Twitter messages as only a “whopping three responses” in a tweet Monday night. But, for legal purposes, just one or two would have been sufficient. Add them to the other contacts with Russia, as well as the president’s publicly stated support for WikiLeaks’ and Russia’s intervention, and the messages confirm that Trump Sr. and his presidential campaign face a “whopping” legal problem.

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