BYRON YORK: After Trump dossier revelation, FBI is next.

Investigators looking into the so-called “Trump dossier” were not surprised when news broke Tuesday night that the Hillary Clinton campaign and the DNC, working through the Democrats’ law firm, Perkins Coie, financed the “salacious and unverified” compilation of allegations of Trump collusion with Russia in the 2016 presidential campaign. (The “salacious and unverified” description comes from former FBI Director James Comey.)

There had been plenty of talk about the Democrats and Perkins Coie, so much that investigators almost assumed that was the case. But it wasn’t until the Washington Post broke the story that it was confirmed.

“I’m shocked,” one lawmaker joked Tuesday night. “Who could have ever guessed?”

And why did the story break when it did? Credit the much-maligned Rep. Devin Nunes, chairman of the House Intelligence Committee. The California Republican has been pursuing the dossier more aggressively than anyone else, and it was his Oct. 4 subpoena for the bank records of Fusion GPS, the opposition research firm that handled the dossier, that finally shook loose the information.

But knowing that the Clinton campaign, the DNC, and Perkins Coie supported the dossier is not the end of the story. The most important next step is the FBI.

Sometime in October 2016 — that is, at the height of the presidential campaign — Christopher Steele, the foreign agent hired by Fusion GPS to compile the Trump dossier, approached the FBI with information he had gleaned during the project. According to a February report in the Washington Post, Steele “reached an agreement with the FBI a few weeks before the election for the bureau to pay him to continue his work.”

It was an astonishing turn: the nation’s top federal law enforcement agency agreeing to fund an ongoing opposition research project being conducted by one of the candidates in the midst of a presidential election.

People should be fired — and, quite possibly, prosecuted — over this.