Washington (CNN) James Comey, anointing himself as America's moral conscience, called on the nation to recognize that Donald Trump's actions add up to an immoral, malignant presidency that insults core democratic values.

Comey set up an unprecedented public challenge from someone of his stature to a sitting commander in chief, framing the most penetrating critique of Trump's White House yet from an establishment figure.

"The foundation of this country is in jeopardy when we stop measuring our leaders against that central value of the truth," Comey said in an exclusive interview with ABC News chief anchor George Stephanopoulos.

His indictment came at the start of a media blitz to promote his book "A Higher Loyalty," publishing Tuesday -- 11 months after he was fired. The action sparked claims the President was trying to obstruct justice over the Russia probe and led to the appointment of a special counsel.

The former FBI director's appearance threw into focus questions that will be at play over the next 10 days: Which version of events will Americans find most credible -- that of the former FBI director or the man who fired him? Will Comey's healthy sense of his own ego and place in history serve to alienate any undecided Americans rather than convince them of his arguments about Trump?

And -- ultimately -- will there be a political price to pay for the President?

The media buzz around the interview and its Washington reverberations could also carry consequences. The New York Times published a full-page op-ed reminding the President he's not above the law, a reminder of how real fears of a systemic political crisis in the event Trump attempts to fire special counsel Robert Mueller or Deputy Attorney General Rod Rosenstein, who is overseeing his probe.

Polarized opinions

Another issue is whether Comey's critique about the President can penetrate the permanent storm that whirls around Trump and fundamentally reshape already polarized opinion about the President's behavior.

recent ABC News poll showed that Americans found Comey more believable than Trump, by a margin of 48% to 32%. If the fierce campaign by Trump world to discredit the former FBI director's book fails to shift that number, it could suggest that the President is in for lasting political damage.

But it's not as if Comey's view of the President represents a sudden shock to the electorate. For example, his descriptions of a President prone to lying are borne out by the facts of the last 15 months. The picture he paints of an almost feudal patriarchy presided over by Trump appears to be validated by the way the President casually fires aides on Twitter and undermines his top aides.

Still, most criticisms of the President by elites like Comey merely serve to solidify the views of his supporters that he is being unfairly maligned.

Comey called for a national moment of reflection, in which everybody, regardless of partisan views, to evaluate the President and to consider whether he presents a threat to America itself.

The simplicity of that challenge seemed an attempt to cut through the chaos, recriminations, wild mood swings and political meltdowns of the last 15 months, in which perspective has often been the victim of the next outrage.

Comey discounted previous theories by some Trump critics that the President is incapable or not mentally up to the job, arguing that what he sees as an ego-driven presidency based on lies, demands for loyalty from subordinates and calculated deceit is no accident.

"He strikes me as a person of above average intelligence who's tracking conversations and knows what's going on. I don't think he's medically unfit to be president. I think he's morally unfit to be president," Comey said.

"A person who sees moral equivalence in Charlottesville, who talks about and treats women like they're pieces of meat, who lies constantly about matters big and small and insists the American people believe it, that person's not fit to be president of the United States, on moral grounds," Comey said.

Comey stressed that he was not making a political point, saying he did not care what people thought about hot button issues like guns or immigration.

"There's something more important than that that should unite all of us, and that is our president must embody respect and adhere to the values that are at the core of this country. The most important being truth," he said. "This president is not able to do that. He is morally unfit to be president."

Contrast in character

Comey's deliberative, forensic manner contrasted to the emotional, angry tirades in which his nemesis, Trump, prefers to communicate was on display on another extraordinary day in the melodrama of the current presidency.

"Slippery James Comey, a man who always ends up badly and out of whack (he is not smart!), will go down as the WORST FBI Director in history, by far!" Trump wrote on Twitter Sunday.

Slippery James Comey, a man who always ends up badly and out of whack (he is not smart!), will go down as the WORST FBI Director in history, by far! — Donald J. Trump (@realDonaldTrump) April 15, 2018

Comey's interview also laid bare the most fundamental clash between him and the President. The former FBI director is a man who reveres the institutions of justice and government. Trump has shown by his behavior and public comments -- for instance by bemoaning how he can't control the Justice Department -- that he sees them as symptoms of a corrupt establishment.

Even so, Comey said his preferred solution to the Trump presidency would not be impeachment, but a rejection by voters.

"I think impeaching and removing Donald Trump from office would let the American people off the hook and have something happen indirectly that I believe they're duty bound to do directly," Comey said. "People in this country need to stand up and go to the voting booth and vote their values."

The interview did not appear to contain any significant new information relevant to the questions at the center of Mueller's investigation over alleged collusion between Trump's 2016 campaign and Russia and whether the President obstruct justice.

But Comey also would not rule out the possibility that Trump was compromised by a Russian intelligence operation.

"It is stunning and I wish I wasn't saying it, but it's just -- it's the truth. I cannot say that. It always struck me and still strikes me as unlikely, and I would have been able to say with high confidence about any other President I dealt with," Comey said. "But I can't, it's possible."

He went a step further in an interview with USA Today that was released shortly after the ABC sitdown aired.

"There's a non-zero possibility that the Russians have some, some sway over him that is rooted in his personal experience, and I don't know whether that's the business about the activity in a Moscow hotel room or finances or something else," he said.

The hotel room reference was apparently in regard to a claim that Russian authorities recorded Trump watching prostitutes urinate in a hotel suite. The allegation was included in a dossier -- portions of which remain unconfirmed -- that was commissioned as opposition research during the 2016 election and compiled by a former British intelligence agent, Christopher Steele.

There is no indication that such a tape exists and Trump has vehemently denied it.

Holier than thou?

JUST WATCHED Trump unloads on Twitter at Comey Replay More Videos ... MUST WATCH Trump unloads on Twitter at Comey 01:44

Comey's book, and the media tour on which he is embarking, is also highlighting some of the criticisms of his own character and behavior which are helping to shape the Trump team's pushback against him.

While he may not deserve to be branded a "slimeball," as Trump did on Sunday, Comey does risk coming across as a disgruntled ex-employee and someone seeking vengeance for his dismissal. He has a highly developed sense of his own morality and sometimes comes across as holier than thou.

He is also raising the question of whether he is further damaging the FBI's creed of being apolitical by mounting such a frontal attack on a sitting President.

The fierce counter-attack by Trump, the White House and the Republican National Committee is less an attempt to defend the President's behavior or dispute Comey's points than to raise questions about his integrity and motivation in order to devalue his devastating takedown of Trump.

"James Comey's publicity tour reaffirms that his true higher loyalty is to himself," said RNC Chairwoman Ronna McDaniel in a statement issued at the end of the ABC News show on Sunday night. "The only thing worse than Comey's history of misconduct is his willingness to say anything to sell books. He has no credibility and President Trump was right to follow through on the bipartisan calls for him to be fired."

Trump's team has seized on Comey's admission that he reopened the investigation into Hillary Clinton's emails days before the election because he thought she would win and did not want her to be compromised as president by the idea that the FBI concealed the fact it was still investigating her.

"The guy knew exactly what he was doing. He thought Hillary Clinton would win. And he thought this would give him some cover," said White House press secretary Sarah Sanders on ABC News "This Week" on Sunday.

"When the person that is supposed to lead the highest law enforcement agency in our country starts making decisions based on political environments instead of on what is right and what is wrong, it's a really dangerous position," she said.