With one word -- "spying" -- Barr on Wednesday ingratiated himself with his new boss, gave fresh life to a conservative media narrative and obliterated any remaining chance that he can now be seen as a good faith arbiter of the Mueller report

Barr set off a Washington firestorm by saying on Capitol Hill on Wednesday that he planned to review US intelligence investigations conducted on the Trump campaign in 2016 at a time when Russia was interfering in the presidential election.

"I think spying on a political campaign is a big deal," Barr said in a congressional hearing, deliberately or not, playing into claims that Trump's campaign was unfairly targeted by the FBI. "I think spying did occur."

The comment, for which the nation's top law enforcement official did not offer evidence, instantly handed Trump a fresh payoff for picking Barr to effectively oversee probes into his campaign's conduct.

That's because Trump claims Robert Mueller's investigation was a "hoax" and an illegal attempt to overthrow his presidency by a "deep state" conspiracy -- claims relentlessly amplified by conservative media cheerleaders.

Former Director of National Intelligence James Clapper, who had a long career serving Republican and Democratic presidents, told CNN's Anderson Cooper that Barr's use of the word "spying" was "both stunning and scary."

"I have to believe he chose that term deliberately," said Clapper, who was part of the senior intelligence leadership at the end of the Obama administration, when US authorities grew concerned about the activities of some Trump campaign aides.

Barr's performance over two days of congressional testimony has revived a debate about his motivation and whether he is trying to protect the rule of law or the President.

A comprehensive judgment will have to await his release of the redacted Mueller report, expected in the next week. But he has significantly raised the stakes.

"I was among those who wanted to give him the benefit of the doubt when he came in," said David Gergen, a former adviser to presidents on both sides of the aisle who is now a senior CNN political analyst.

"I just felt he would just want to protect his reputation for integrity and would want to show that he was independent ... and he has now repeatedly acted in ways that have called all of that into question."

Pelosi pounces

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Democrats who were already fuming that Barr last month chose to deliver Mueller's "bottom lines," which appeared favorable to the President, in advance of a redacted version of his final report, reacted furiously to his comments.

House Speaker Nancy Pelosi made a case that Barr could not be trusted to observe the traditions of political independence implied in the job of attorney general.

"Let me just say how very, very dismaying and disappointing that the chief law enforcement officer of our country is going off the rails, yesterday and today," Pelosi said.

"He is the attorney general of the United States of America, not the attorney general of Donald Trump," she added.

Democratic House Intelligence Chairman Adam Schiff warned that Barr should not "casually suggest" that those under his charge had spied on a political campaign and that the comment had struck "another destructive blow to our democratic institutions."

Wednesday's controversy will also fuel suspicions among Democrats and some legal analysts that Barr -- who was on the record before his appointment as skeptical that it was possible for Trump to commit obstruction of justice -- is already politicizing the Justice Department and shielding the President.

Those worries have been exacerbated by his refusal to hand over a full version of the Mueller report and supporting evidence gathered by the special counsel to Congress.

His comments will also bolster concern that the Justice Department may be preparing to act on the President's demands for vengeance against his foes, including ex-FBI Director James Comey, who was overseeing the Russia investigation when he was fired.

There is also the question of why Barr intends to carry out his own review of what happened in 2016 when there is already a departmental inspector general's investigation underway on the issue.

Barr later tried to qualify his comments, saying he was not trying to say "improper surveillance occurred" but that he wanted to review the matter to ensure any surveillance was justified.

He failed, however, to quell speculation about his motives in Washington.

Was he deliberately seeking to signal that he had the President's back? Was he intending to create some political space for himself with a boss who is no doubt frequently in his ear about going after his political opponents? Or was he simply the victim of his own clumsy word choice and unaccustomed to a vicious political climate that has turned toxic since he served in the same job for President George H.W. Bush?

Trump capitalizes on 'spying' storm

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But in the hyperbolic atmosphere fostered around the Mueller probe by Trump, all nuance is already lost.

"When I heard 'spying,' my heart skipped a beat," said Harry Litman, a former deputy assistant attorney general, on CNN.

"That is a loaded term -- Bill Barr knows it's a loaded term and was likely to play into a triumphant talking point from President Trump," Litman said.

Former federal prosecutor Jennifer Rodgers said Barr was using the word "spying" in a way that sounded worse than he intended.

"I think really he means surveillance," she told CNN's Kate Bolduan.

Ever sensitive to a political opening, it did not take long for the President to appear before cameras to capitalize on the moment.

"What has been found during this period of time are the illegal acts of getting this whole phony investigation started," Trump told reporters. "What they did was treason. What they did was terrible."

The Justice Department inspector general is looking into allegations that the FBI abused its powers in surveilling former Trump foreign policy aide Carter Page, among other issues.

The bureau issued a heavily redacted Foreign Intelligence Surveillance Act warrant last year that it obtained for Page in October 2016 -- after he had left the Trump campaign.

It says that the FBI "believes Page has been the subject of targeted recruitment by the Russian government."

"The FBI believes that Page has been collaborating and conspiring with the Russian government," the application said.

Trump's allies have also sought to argue that the FBI unfairly opened an investigation into the Trump campaign after seizing on a dossier compiled by former British intelligence officer Christopher Steele that alleged the then-Republican nominee was compromised by Russia. Some, though not all, of the dossier's claims have been verified.

Fresh assault

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Barr's comments will fuel a fresh assault by Trump's allies who have spent months trying to discredit the Mueller report -- and are cranking up the operation again in the expectation that the attorney general will release the redacted version soon.

The opening comes after Trump and the White House, using Barr's letter to Congress summarizing the report, had already cemented a political narrative, declaring falsely that the President was exonerated by Mueller and that the special counsel had found no collusion or obstruction of justice.

The media offensive has in many cases drowned out Mueller's evidence that the President was the beneficiary of a Russian intelligence operation to interfere in the US election and harm his opponent, Hillary Clinton.

Though Barr said in the letter to Congress that the Mueller report did not establish there was collusion between the Trump campaign and Russia, multiple members of the President's team had contacts with Russians and later lied about them.

Barr also told lawmakers in the letter that while Mueller did not reach a conclusion on whether Trump had obstructed justice, he and Deputy Attorney General Rod Rosenstein concluded the evidence was not sufficient to establish that the President had done so.

CNN Justice Correspondent Laura Jarrett quoted a source familiar with the attorney general's thinking as saying Barr meant the word "spying" in the classic sense of intelligence collection and had not meant to throw red meat to conspiracy theorists.

The source emphasized repeatedly that Barr is focused on whether there was proper "predication" for any surveillance -- as he said in the hearing.

If Barr was seeking to put himself on good terms with the President, it is not clear how long he will remain a favorite.

Given the careful nature of his language in his letter about the Mueller report, it remains a high possibility that although it may not show criminal wrongdoing, the special counsel's evidence could still be deeply damaging to the President.

Barr testified on Wednesday that Mueller did not ask him or Congress to come to a determination on whether Trump obstructed justice but concluded there was not a case to prosecute.

It is far from clear that top Democratic leaders -- though wary of embarking on an impeachment case -- will draw the same conclusions from the Mueller report as Barr.