Washington (CNN) The gravity and drama of the first televised impeachment hearings into Donald Trump's presidency on Wednesday will imprint themselves on history and reverberate far from Washington.

The most crucial stage of the Ukraine investigation so far has profound implications beyond the political and personal reputation of Trump and the question of whether he abused his power by seeking political favors from a foreign power.

His fate will have sweeping consequences for the future understanding of powers vested within the presidency itself. The hearings will test whether the ancient machinery of US governance can effectively investigate a President who ignores the charges against him and fogs fact in defining a new post-truth political era . And notwithstanding Trump's current Republican firewall, the hearings will begin to decide whether a presidency that has rocked America and the world will reach its full natural term.

The fact that there is an impeachment process at all -- and a debate over whether the President is so corrupt he should be ousted between elections -- is in itself something of a national tragedy. There's a reason why Gerald Ford called the Watergate scandal that led to the resignation of President Richard Nixon in 1974 before he was formally impeached, a "long national nightmare."

The next few months will scar America for years to come. As the Bill Clinton and Andrew Johnson impeachments did before it, this process will reflect and intensify the ideological civil war that is tearing at national unity and threatening the nation's forward momentum.

Democratic leaders, who long resisted demands from their party's liberal activists to impeach Trump, are taking a considerable risk by embarking on this momentous constitutional road. Given the explosive revelations about Trump's conduct in Ukraine however, they may have had little political choice.

In all likelihood, Republican senators will not vote to convict and oust Trump, opening the possibility of a political backlash. It's just not clear yet whether Democrats or the GOP would come off worse. Trump is likely to view an eventual escape from censure as a validation of his unrestrained behavior and a license to continue to test constitutional customs.

The case against Trump

"I've always thought that the strongest argument for impeachment was also the strongest argument against it, which is, if you don't impeach a president who commits conduct of this kind, what does that say to the next president about what they can do and to the next Congress?" House Intelligence Chairman Adam Schiff said in an interview with National Public Radio on Tuesday.

"At the same time, if you do impeach, but the President is acquitted, what does that say to the next president? The next Congress? There's no good or simple answer," he said.

Yet for all the bitterness and uncertainty that it stirs, the impeachment process is also a reaffirmation and test of the democratic codes of self-government first set down in Philadelphia nearly two-and-a-half centuries ago.

It will provide the most significant judgment yet on a riotous presidency that has already skipped past one existential scandal in the Russia election meddling scheme

The Democratic charge that could see Trump shamed as only the third impeached President in history could hardly be more grave. He is effectively accused of committing a crime against the nation itself and the political system that guards its freedoms.

Specifically, Democrats charge Trump with conspiring with a foreign power to influence a US election, an offense many observers believe satisfies the impeachable standard of "Treason, Bribery or other high crimes and misdemeanors."

The eventual case may encompass campaign finance offenses, the flouting of his presidential oath to uphold the law and the Constitution and allege obstruction over his withholding of witnesses and evidence. In more symbolic terms, it would validate the fears of America's founders of one of the greatest threats to their democratic experiment.

"History and experience prove that foreign influence is one of the most baneful foes of republican government," wrote the first President, George Washington, in his farewell address.

The Democratic tactics

To force Trump's removal from office, Democrats must use the hearings beginning on Wednesday to turn independents and moderate Republicans against him.

They hope that the testimony of witnesses including foreign service lifers such as Bill Taylor, the top US diplomat in Kiev , who opens proceedings on Wednesday, will come across as credible and defang the GOP counterattack. They will portray ousted US Ambassador to Ukraine Marie "Masha" Yovanovitch , who will testify on Friday, as a victim of Trump's scheme to benefit himself and not US national interests.

They are striving to change the political calculation of GOP senators currently unlikely to desert Trump and build the two-thirds majority to convict him in a Senate trial. Failing that, Trump could be so damaged by impeachment that his hopes of breaking out beyond his base in the 2020 will be doomed.

In essence, Democrats are seeking to build made-for-TV moments that can tell the story of the Ukraine scandal in simple terms -- as the Senate Watergate hearings did in the Nixon era.

It is unclear whether they have a witness to match the impact of former White House counsel John Dean, who testified that he told Nixon that "there was a cancer growing on the presidency."

Democrats argue Trump built a sophisticated back-door diplomatic effort to pressure Ukraine to investigate former Vice President Joe Biden and his son Hunter and a conspiracy theory that Kiev and not Russia meddled in the 2016 election. There is no evidence of wrongdoing in Ukraine by either Biden.

Democrats allege that the quid pro quos in this equation involved $400 million in delayed military aid to Ukraine and conditions initially imposed on a White House visit for its President, Volodymyr Zelensky.

Democrats have also collected evidence that Trump's personal lawyer Rudy Giuliani was barnstorming around in Europe trying to close the deal with Ukraine and bypassing US diplomats.

"Go talk to Rudy, he knows all about Ukraine," GOP mega-donor turned US Ambassador to the European Union Gordon Sondland testified that Trump told his subordinates.

Trump has refused to produce, or Democrats have declined to launch long legal challenges to access, key witnesses who could establish or rule out any direct link with the President.

Yet acting White House chief of staff Mick Mulvaney effectively confirmed a quid pro quo with Ukraine over military aid in a stunning White House briefing that included the words: "Get over it."

Ultimately, the Democratic appeal to the American people will come down to this: Is it credible that all this was going on and Trump did not direct it -- or at least knew all about it?

The Republican defense

Since the Ukraine scandal erupted, Republicans have struggled to coin a consistent defense of the President.

His rough transcript of the call with Zelensky backfired as it was far from "perfect" as Trump said it was.

A flow of leaked witness testimony has deepened Trump's trouble. In response, the GOP has demanding the unmasking of a whistleblower in the intelligence community that first raised the alarm about Trump's call with Zelensky.

Republicans on the House Intelligence Committee are certain to stage sideshows to thwart Democratic hopes of presenting the public with a clear narrative.

Democrats have struggled to stop previous high-profile hearings from turning into circuses. This time, Schiff has decreed witnesses will first be questioned by professional counsel from both sides -- at least delaying political hijinks.

In a strategy memo released on Monday , GOP House members signaled they would argue that there was no coercion in the Trump-Zelensky call. They say that the fact military aid was eventually released in September means there is no case to answer and that it was Trump's skepticism of corruption in Ukraine that led him to delay it in the first place.

Each point is debatable. Perhaps that's one reason why Trump is desperate to discredit the impeachment probe just as he did with Robert Mueller's special counsel investigation.

The President is flooding the zone with a characteristic trove of conspiracy theories, outright lies, distractions and misinformation designed to confuse the public and fog clarity.

Yet an impeachment hearing is such a profound moment that the President's normal weapons may not work so well this time.

"The Republicans have staked their defense on a variety of techniques that don't address the charges. They claim this a biased investigation, that this is a witch hunt," said Claire Finkelstein, faculty director at the Center for Ethics and the Rule of Law at the University of Pennsylvania Carey Law School.

The Republican approach is essentially a bet that their hurricane force rhetoric will obscure the seriousness of the charges that are being presented to the public.

"There are some signs this is wearing thin for the American people and that they are actually attending to the content of the investigations," Finkelstein said.

"Once the public hearings begin the public will focus on the actual charges. That is what happened with Nixon in the Watergate hearings."