Washington (CNN) Scandals, large or small, mark most American presidencies. What makes Donald Trump historically unique is something different.

Brazenly, Trump disdains even the idea that moral or ethical norms shape his conduct or define the nation he leads. He rejects distinctions between right and wrong for an ethos of explicit self-interest that Americans have never before seen from the White House.

Trump questioned the Catholic faith of House Speaker Nancy Pelosi, and ridiculed the grief of a widow who voted for his impeachment. He derided Utah Sen. Mitt Romney for "sanctimoniously" declaring that his oath before God compelled his Senate trial vote to convict Trump.

The President didn't stop at firing national security aide Alexander Vindman. Trump, who as a young man escaped Vietnam War service by claiming he had "bone spurs," mocked Vindman's military record, which earned him a Purple Heart for wounds suffered during Iraq War combat.

"You think I'm supposed to be happy with him?" Trump asked reporters. "I'm not."

The overt transactional reasoning behind Trump's conduct sets his presidency apart. Whatever their failings, his predecessors made the White House what Franklin Roosevelt called "a place of moral leadership."

"We've had presidents who were more moral, or less moral," said Pete Wehner, who held a senior White House post under President George W. Bush. "We've never had a president who takes psychic delight in shattering moral norms, or discrediting morality as a concept."

Long history

Trump disdained notions of virtue long before his presidency. He dubbed his youthful battle to avoid sexually transmitted diseases "my personal Vietnam." Fifteen years ago, he bragged about behavior that amounts to sexual assaults on women, claiming that "when you're a star they let you do it." He has subsequently denied any actual misconduct and later dismissed the comments as "locker room talk."

He told The New York Times he withdrew medical assistance for a young relative with cerebral palsy to retaliate for a lawsuit filed by the child's father. After suing a journalist who cast doubt on his business record, he admitted some boasts at issue came from "mental projections" rather than actual analysis.

In the 2016 campaign, Trump put these qualities on a larger stage. He maligned John McCain's experience as a Vietnam War prisoner, and embraced torture as a military tool.

He mimicked a disabled reporter who questioned the truthfulness of his recollections about 9/11. He belittled the parents of a soldier killed in Iraq after they criticized his attacks on Muslims.

He ridiculed the poll standing and physical stature of Republican rivals Lindsey Graham and Marco Rubio. He insulted Ted Cruz' wife, and baselessly linked Cruz' father to the assassination of President John F. Kennedy.

"The man is utterly amoral," Cruz eventually fumed. "Morality does not exist for him."

Unbowed by presidency

Those who hoped the grandeur of the Oval Office would change him have been disappointed.

Trump has complained about the unfairness of a law barring American businesses from bribing foreign government officials. He defended seeking help from Russians on grounds that any campaign would -- and signaled he'd do it again.

President Abraham Lincoln once looked beyond the Civil War "with malice toward none, with charity for all." Trump says the Ukraine ambassador he fired would "go through some things," and impeachment adversary Adam Schiff "has not paid the price yet."

Kennedy vowed America would "pay any price, bear any burden" to safeguard freedom. Trump questions the worth of international defense commitments, insisting other countries have played the US for suckers.

"I want to take everything back from the world that we've given them," he once said.

Ronald Reagan called America "a shining city on a hill." After an interviewer called Russian autocrat Vladimir Putin "a killer," Trump replied: "You think our country's so innocent?"

Barack Obama used his final prayer breakfast to call for humility and "pray that my failings are forgiven." Trump last week cited poll numbers and stock values while boasting, "we're setting records that nobody thought achievable."

Never changing

Wehner, an evangelical Christian, concludes the President can't help it.

"Asking Trump to understand morality is like asking a person born blind to understand color," the former Bush aide said.

Other presidents who flagrantly transgressed paid homage to virtue. Bill Clinton apologized to the Republican-controlled Congress that impeached him, confessing to Americans: "I have sinned." Richard Nixon hailed the nation's generosity and self-sacrifice as he became the only president ever to resign.

Americans don't expect that from Trump. Solid majorities have consistently told Quinnipiac University pollsters that he is not honest, does not care about average Americans and is not a good role model for children.

Yet Trump has compelled fealty from fellow Republicans nevertheless. Ironically, one reason is fear that, without solidarity, what Attorney General Bill Barr calls "militant secularists" will overrun the party of traditional values and produce "moral chaos."

Consider the ex-primary rivals Trump savaged. After the Ukraine scandal broke, Graham, Rubio and Cruz all signaled concern about a potential aid-for-investigations quid pro quo but called it unproven.

By the end of the Senate trial, Cruz privately told White House lawyers that all 100 senators believed Trump demanded a quid pro quo. But like Graham, Rubio, and all Republicans except Romney, Cruz insisted it did not merit removal from office and voted to acquit him.

Cruz joined Trump at the prayer breakfast the next day.

"Together," the Texas senator tweeted, "we prayed for unity, for the strength to love our enemies, and for God to heal our land."