KIMBERLEY STRASSEL: The Democrats’ ‘Russian Descent:’ Tactics in the Trump probe are starting to look a lot like McCarthyism.

Democrats have spent weeks making the case that the Russia-Trump probes need to continue, piling on demands for more witnesses and documents. So desperate is the left to keep this Trump cudgel to hand that Senate Intelligence Committee Democrats have moved toward neo- McCarthyism.

If that sounds hyperbolic, consider an email recently disclosed by the Young Turks Network, a progressive YouTube news channel. It’s dated Dec. 19, 2017, and its author is April Doss, senior counsel for the committee’s Democrats, including Vice Chairman Mark Warner.

Ms. Doss was writing to Robert Barnes, an attorney for Charles C. Johnson, the controversial and unpleasant alt-right blogger. Mr. Johnson’s interactions with Julian Assange inspired some in the media to speculate last year that Mr. Johnson had served as a back channel between the Trump campaign and WikiLeaks. There’s still no proof, but in July the Intelligence Committee sent a letter requesting Mr. Johnson submit to them any documents, emails, texts or the like related to “any communications with Russian persons” in a variety of 2016 circumstances, including those related to “the 2016 U.S. Presidential Campaign.”

Mr. Barnes seems to have wanted clarification from Ms. Doss about the definition of “Russian persons.” And this would make sense, since it’s a loose term. Russians in Russia? Russians in America? Russians with business in the country? Russians who lobby the U.S. and might be affected by the election—though not in contact with campaigns?

Ms. Doss’s response was more sweeping than any of these: “The provision we discussed narrowing was clarifying that the phrase ‘Russian persons’ in [the committee letter] may be read to refer to persons that Mr. Johnson knows or has reason to believe are of Russian nationality or descent” (emphasis added).

Well, to be fair, it was the Democrats who imprisoned people in concentration camps simply for being of Japanese descent, so at least they’re consistent.