A tantalizing new report from Shane Harris of the Wall Street Journal gives the strongest indication yet that collusion may have occurred — or was at least attempted — between supporters of Donald Trump's 2016 presidential campaign and Russian hackers who targeted Democrats' emails.

And it raises serious questions about whether fired National Security Adviser Michael Flynn was involved in these efforts to contact hackers.

Harris describes an effort by Peter Smith, a Trump-supporting GOP operative and private equity executive, to track down Hillary Clinton's infamous 30,000 or so deleted emailsduring the fall of 2016.

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The effort, described on the record to Harris by Smith (the 81-year old man died a week and a half after their interview), entailed outreach to several hacker groups, including at least two that Smith believed to be Russian-tied, to see if they had hacked the emails and could release them.

The emails — which Clinton said she deleted because they were personal and unrelated to her work as secretary of state — never surfaced. And Smith didn't work for the Trump campaign.

But this new report could be especially significant because of one name that keeps coming up: Michael Flynn, who at the time was advising the Trump campaign.

Smith repeatedly claimed that he was in contact with Flynn about the effort to find Clinton's emails, per Harris's sources.

"He said, 'I'm talking to Michael Flynn about this — if you find anything, can you let me know?'" said Eric York, a computer-security expert from Atlanta who searched hacker forums on Mr. Smith's behalf for people who might have access to the emails. ... ... In phone conversations, Mr. Smith told a computer expert he was in direct contact with Mr. Flynn and his son, according to this expert. ... The expert said that based on his conversations with Mr. Smith, he understood the elder Mr. Flynn to be coordinating with Mr. Smith's group in his capacity as a Trump campaign adviser.

Furthermore, Harris describes, apparently for the first time, US intelligence reports claiming Russian hackers discussed how to get hacked emails to Flynn through a third party.

Investigators have examined reports from intelligence agencies that describe Russian hackers discussing how to obtain emails from Mrs. Clinton's server and then transmit them to Mr. Flynn via an intermediary, according to U.S. officials with knowledge of the intelligence.

If accurate, all this is enough to raise serious questions about just what Flynn knew about this or any other attempted outreach to Russian hackers.