Democrats and some in the media expressed shock and outrage when Attorney General William Barr said Wednesday that "spying did occur" on the Trump campaign during the 2016 election.

Barr "must retract his statement immediately or produce specific evidence to back it up," Senate Minority Leader Chuck Schumer said. "Perpetuating conspiracy theories is beneath the office of the attorney general."

Barr has gone "off the rails," said House Speaker Nancy Pelosi.

"The attorney general must retract his unfounded, irresponsible claim," said Democratic Sen. Richard Blumenthal.

Cable news commentators called Barr's statement "stunning" and appeared baffled that the attorney general would make such a claim "without evidence."

The baffling thing was why they were baffled. Barr's statement was accurate and supported by publicly known facts.

First, what Barr said. "I think spying did occur," he told the Senate Appropriations Committee. "But the question is whether it was adequately predicated. And I'm not suggesting it was not adequately predicated. But I need to explore that."

That is entirely accurate. It is a fact that in October 2016 the FBI wiretapped Carter Page, who had earlier been a short-term foreign policy adviser to the Trump campaign. The bureau's application to a secret court for that wiretapping is public. It is heavily redacted but is clearly focused on Page and "the Russian government's attempt to influence the 2016 U.S. presidential election." Page was wiretapped because of his connection with the Trump campaign.

Some critics have noted that the wiretap authorization came after Page left the campaign. But the surveillance order allowed authorities to intercept Page's electronic communications both going forward from the day of the order and backward, as well. Investigators could see Page's emails and texts going back to his time in the campaign.

So there is simply no doubt that the FBI wiretapped a Trump campaign figure. Is a wiretap "spying"? It is hard to imagine a practice, whether approved by a court or not, more associated with spying.

That alone is enough to back up Barr's remark. But it is also known that the FBI engaged at least one informant, a professor named Stefan Halper, to penetrate the Trump campaign. The New York Times recently reported, "Agents involved in the Russia investigation asked Mr. Halper, an American academic who teaches in Britain, to gather information on Mr. Page and George Papadopoulos, another Trump campaign foreign policy adviser."

Halper went beyond Page and Papadopoulos, also contacting and seeking information from Trump campaign aide Sam Clovis. "It was not clear whether Mr. Halper had the FBI's blessing to contact Mr. Clovis," the Times said.

The Halper case is more evidence that "spying did occur" on the Trump campaign during the 2016 election. At least in the cases of Page and Papadopoulos, the information gathering was done by an informant engaged by the FBI.

As to the second part of Barr's statement, "The question is whether it was adequately predicated," meaning whether the FBI presented evidence sufficient to justify surveillance, that is something that has been the subject of intense public debate. When the heavily blacked-out Page surveillance application was released — over the strong objections of the FBI — there followed a passionate argument over whether the wiretapping was "adequately predicated."

Republicans argued that it was not, because the application was based in part on the Steele dossier, the collection of unverified opposition research allegations compiled by British spy Christopher Steele on behalf of the Hillary Clinton campaign. Democrats argued that the application was done properly and that the Page surveillance was justified. So, just as Barr said, the question was whether the spying was "adequately predicated."

There has been less public debate over whether the Halper operation was "adequately predicated."

In any event, despite the cries from outraged Democrats and the media analysts who simply can't imagine what Barr might have been referring to, the attorney general's words were demonstrably true.