Washington (CNN) Donald Trump 's entire life story of fighting and surviving, of cheating personal and professional ruin over and over, has delivered him to his greatest battle yet -- the one to save his presidency.

Trump is facing down a swarm of investigations f rom multiple congressional committees, a special counsel, state and federal prosecutors, and private litigants. His entire life is under scrutiny.

But the fight back has begun.

If there is any President who could bear such strain, who would perhaps relish the struggle, prosper amid its cacophony and be willing to cross all sorts of conventional lines to stay alive, it would surely be Trump.

As a youth at New York Military Academy, the future President learned one thing above all else: "life is about survival. It's always about survival," according to writer Michael D'Antonio in his biography of Trump.

It's been Trump's motto ever since, no matter the collateral damage and the cost of legal battles and reputational hits, personal scandals and bankruptcies.

Now America is about to be dragged along on Trump's most existential struggle yet. Survival in a personal and political sense now defines his life, with Robert Mueller's report expected to be filed soon and Democrats unfurling an oversight blitz that could lead to impeachment.

When House Democrats on Monday unveiled a mammoth document demand from a list of 81 potential witnesses linked to Trump's businesses, campaigns, presidency and family, he and aides initially pledged cooperation.

But the mask soon slipped.

Trump responded on Tuesday according to his creed, with a promise of all-out confrontation and a searing blast at his enemies.

"It's a disgrace. It's a disgrace to our country," he said, accusing Democrats of being consumed by anger at their loss in 2016, and framing the coming fight as an extension of his 2020 re-election campaign.

Trump's press secretary, Sarah Sanders, set the vituperative tone of a fight against a Democratic majority seeking to expose the President as historically corrupt.

"Democrats have embarked on a fishing expedition because they are terrified that their two year false narrative of 'Russia collusion' is crumbling," Sanders said in a statement on Monday night. "The Democrats are not after the truth, they are after the President."

An enemy in his sights

Sanders and everyone else inside the White House are about to endure the bitter, full-on misery of a multi-front oversight campaign. That means a blizzard of subpoenas, officials being hauled up to Capitol Hill to testify under penalty of perjury and a mountain of legal bills.

But Trump has lived in the eye of such storms for much of his adult life, and he comes to the fight with certain advantages.

His clash with House Democrats will give him the foil in the form of his Democratic tormentors that he's lacked ever since his 2016 campaign. This President is always most effective with an enemy to define himself against.

The duel will serve to unite the Republican Party in Washington behind the President -- amid some signs of cracks opening in the GOP edifice in the Senate, at least, over his national emergency declaration.

It will be a rallying moment that will enrage and enthuse Trump's base ahead of the 2020 campaign. That may mean he can avoid risky strategies, such as the disastrous government shutdown, to keep his troops motivated.

Republicans are already working off the Trump playbook, which is designed to present him as the victim of unfair presidential persecution by Democrats.

"He just believes they are out to take a wrecking ball to his life," Republican Sen. Lindsey Graham of South Carolina said Tuesday after meeting the President. "They'll go nuts."

Republican Sen. John Cornyn of Texas warned that the Democratic investigation was less about finding the truth and more about ousting a President.

"It's all about setting up the stage for impeachment proceedings. That's pretty clear," Cornyn told CNN's Manu Raju.

Republicans make such arguments in the knowledge that the nation, despite Trump's unpopularity and widespread suspicions about his conduct, is not yet ready for the trauma of the third impeachment drama in 50 years.

Still, a new Quinnipiac University poll shows a public appetite for investigations. Some 64% of respondents thought Trump had committed crimes before he became President. Even 33% of Republicans thought so. But Trump's approval rating among GOP voters still stood at 82%, suggesting that some of their numbers think he's a criminal but don't care.

But only 35% of those polled thought that Democrats should initiate impeachment proceedings against the President -- a number that explains the party's caution in the messaging around its investigations.

Did Democrats cast the net too wide?

JUST WATCHED White House refuses to produce security clearance info Replay More Videos ... MUST WATCH White House refuses to produce security clearance info 02:34

Multiple presidential aides told CNN's Kaitlan Collins on Tuesday that they were surprised at the expansive nature of House Judiciary Chairman Jerrold Nadler's document request. The belief is that Democrats -- blasting the White House on multiple fronts -- miscalculated by not making a more targeted opening burst.

Officials are already planning to push back on the expansive witness demands and to preserve what they say is the President's right to confidentiality, a sign that grueling fights are looming over executive privilege.

There were already signs of that strategy rolling into action on Tuesday.

House Oversight Chairman Elijah Cummings complained that the White House had refused requests for documents and witnesses for an inquiry into what he says are security clearance "abuses" in the West Wing.

"The White House's argument defies the Constitutional separation of powers, decades of precedent before this Committee, and just plain common-sense," Cummings said in a statement.

A White House official, however, told CNN's Jim Acosta that the Maryland Democrat was demanding documents he was not entitled to under the law.

The swift escalation of the dispute left the committee to consider whether to issue subpoenas to get information, a step that could spark a legal scenario that could be repeated scores of times in the coming months.

Prolonged legal tussles will not just frustrate Democrats. They will take months, churn all the way through the court system and delay any final accounting for the President -- possibly until the heat of the 2020 campaign.

Executive privilege -- the idea that the President has a right to confidential counsel from top officials -- has not been widely litigated in the courts, meaning that legal cases might eventually make their laborious way all the way to the Supreme Court.

That would suit Trump just fine.

Echoes of Bill Clinton

JUST WATCHED Burnett on the hypocrisy of Trump's refusal to cooperate Replay More Videos ... MUST WATCH Burnett on the hypocrisy of Trump's refusal to cooperate 02:24

The coming battle will be fought on a legal as well as a political front.

Some Washington veterans remember that the Republican impeachment of Bill Clinton in the late 1990s eventually backfired on the party, given that the public didn't believe the President's transgression -- effectively lying under oath about sex -- met the constitutional bar of "high crimes and misdemeanors."

Clinton, with his legendary capacity to compartmentalize, presided over a White House that fought hard against Capitol Hill investigations.

But he also went out of his way to show that he was doing his job, leading the country through a period of economic prosperity, in a way that made efforts to bring him down appear petty and inappropriate.

"These allegations are false and I need to go back to work for the American people," Clinton said in 1998.

One of Clinton's antagonists, who voted as a House member to impeach him, drew lessons from that long-ago fight.

"You just have to put your head down, fight back and govern the country -- that's what Clinton did," Graham said, saying Trump should now challenge the Democrats to "fix problems."

There was more than an echo of Clintonian rhetoric in Trump's public statement on Tuesday, delivered as he signed an executive order tackling an epidemic of suicide among veterans.

"Instead of doing infrastructure, instead of doing health care, instead of doing so many things that they should be doing, they want to play games," Trump said of his Democratic opponents. "It's too bad because I'd rather see them do legislation."

The Clinton parallel may not be exact, however.

At the start of his impeachment drama in 1998, Clinton was far more popular than Trump, with his approval rating measured by Gallup at 58%. He never went below 60% in the brutal year that followed, hit 73% after he was impeached and settled at 66% after he was acquitted in a Senate trial.

According to the Quinnipiac poll, Trump is at 38% approval. And while a recent Wall Street Journal/NBC poll had him at 46%, his numbers rarely move beyond a narrow range, with favorability well below a majority of voters.

That means Trump may not be able to bank on high personal popularity during the most dangerous political moments of his presidency.

His scattershot approach to the office suggests he lacks the discipline that sustained Clinton. And Trump's incessant claims that he is the victim of "hoax" investigations and attempts to tear down the guardrails surrounding his office often give the impression that he has something to hide.

And for all the years of controversies and scandals that plagued Clinton, the 42nd President was never the focus of so many credible civil and criminal investigations as are bearing down on Trump.