If we were ever to get to the bottom of actual collusion in the course of the 2016 election, it would be that of the Democrats with the Fusion GPS smear outfit. Kim Strassel’s Wall Street Journal column updates the story of the appearance of two Fusion GPS principals before the House Intelligence Committee. In “The case of Fusion GPS,” I noted the intention of company witnesses to claim the Fifth Amendment privilege against self-incrimination to maintain their silence. They refuse to tell the committee who paid for the infamous Trump Dossier or whom their clients were. Kim now reports that they proceeded to do just that on Thursday. In the heart of her column Kim explains:

[Fusion GPS is] the firm behind the infamous “dossier” accusing Donald Trump of not just unbecoming behavior but also colluding with Russia. Republicans are investigating whether the Fusion dossier was influenced by Russians, and whether American law enforcement relied on that disinformation for its own probe.

But Fusion’s secret weapon in its latest operation is the Democratic Party, whose most powerful members have made protecting Fusion’s secrets their highest priority. Senate Democrats invoked a parliamentary maneuver in July to block temporarily Mr. Browder’s public testimony. Rep. Adam Schiff, the Democratic ranking member on the Intelligence Committee, has been engineering flaps to undercut and obstruct Mr. Nunes’s investigation. Democrats on the House Ethics Committee have deep-sixed what was meant to be a brief inquiry to clear Mr. Nunes so as to keep him sidelined.

Then there is the intel committee’s meeting this week. Despite the spin, forcing Fusion to appear was Republicans’ only recourse after months of stonewalling. Fusion’s letter ludicrously claimed that Mr. Nunes’s subpoenas were invalid, which essentially forced the committee to show otherwise. It was a question of authority.

Florida Rep. Tom Rooney put the Fusion attendees through a series of questions not out of spite but to clarify finally just what topics the firm is refusing to talk about. The Fifth Amendment doesn’t provide protection against answering all questions. It only protects against providing self-incriminating evidence. It is therefore revealing that Fusion took the Fifth on every topic—from its relationship with British spook Christopher Steele, to the history of its work, to its role in the dossier.

The untold story is the Democrats’ unprecedented behavior. Mr. Rooney had barely started when committee staffers for Mr. Schiff interrupted, accused him of badgering witnesses, and suggested he was acting unethically. Jaws dropped. Staff do not interrupt congressmen. They do not accuse them of misbehavior. And they certainly do not act as defense attorneys for witnesses. No Democratic lawmakers had bothered to come to the hearing to police this circus, and Mr. Rooney told me that he “won’t be doing any more interviews without a member from the minority present.”

Private-sector lawyers also tend not to accuse congressmen of unethical behavior, as Mr. Levy did in his letter to Mr. Nunes. But Fusion’s legal eagle must feel safe. He’s former general counsel to the Senate’s minority leader, Chuck Schumer. He has also, I’m told by people familiar with the committee’s activities, more than once possessed information that he would have had no earthly means of knowing, since it was secret committee business. Consider that: Democratic members of Congress or their staff providing sensitive details of an investigation to a company to which the committee has given subpoenas.