Two pieces of evidence that have come together prove anti-Trump dossier writer Christopher Steele was the key source for a Yahoo News story that the FBI cited to support its wiretap application.

Identifying the source of that September 2016 article on Trump campaign volunteer Carter Page has taken on added importance in recent weeks.

First, Rep. Devin Nunes, California Republican and chairman of the House Permanent Select Committee on Intelligence, issued a declassified memo on Feb. 2. It said the FBI relied greatly on Mr. Steele’s discredited Democrat-financed dossier to obtain a surveillance warrant on Mr. Page.

To bolster the dossier’s charge that Mr. Page met with two Kremlin figures in Moscow, the FBI cited the Yahoo News article, which said the same thing.