Washington (CNN) Donald Trump is four days away from assuming the presidency after one of the most tumultuous transitions in modern history, setting the stage for a rocky period of dramatic change, partisan acrimony and unpredictable results.

Trump will take office with far lower poll ratings than his recent predecessors, with majorities of Americans doubtful of his capacity to handle the job. He's at war with the nation's intelligence agencies , has a dysfunctional relationship with the press , is fighting claims that he's too cozy with Russia and is brushing off conventional ethical standards for an incoming president. China has warned him about changing policy related to Taiwan and Mexico has threatened retaliation if Trump imposes a border tax.

For any other incoming president, such a pile of controversies and crises would suggest an early political disaster is imminent for the new White House. But Trump broke the mold in his outsider campaign and has repeatedly shrugged off scandals and controversies that would have downed normal politicians. He appears determined to shake up conventions that have built up around the presidency for two centuries and has little time for those who say he lacks presidential demeanor.

In fact, many of the political storms raging as he takes office have been instigated by Trump himself. Inciting chaos and disruption has been the key to his political career, helping him rupture the Republican establishment and win the White House. He seemingly has no plans to change tactics in the White House.

"He is reinventing the modern presidency," said Timothy Naftali, a CNN presidential historian.

But as Trump takes office, his signature style, designed to keep everyone off balance, is facing its most significant test. Will his confrontational, brazen approach, the prosecution of personal grudges on social media and tendency to stir disorientation prove to be a workable template for a presidency? And will his method of deliberately picking at societal fault lines work when Trump is president of all Americans?

Metrics for success

"Only time will tell whether he succeeds as a leader," said Naftali, who also teaches at New York University and warns that while Trump often plays by different rules, history will not. "We know the metrics for success haven't changed -- public opinion, bills passed, confidence around the world, confidence at home, a strong economy. All these things are the same metrics."

Trump, he continued, "is reinventing the style of the presidency and every president has the right to do that. But he's going to be tested the same way."

Trump will begin his administration in a deepening hole with public opinion.

His approval rating stood at 44% a week before the inauguration, according to Gallup. President Barack Obama was at 83% at the equivalent moment, George W. Bush was at 61% and Bill Clinton at 68%.

A Pew Research poll found that 39% of Americans approve of the way Trump has outlined his policies while a Quinnipiac poll put his approval rating at 37% last week.

Gallup also found Trump under 50% on questions about whether he will handle military force wisely, how he would steer an international crisis and on his capacity to avoid major scandals in his administration. He does better over his ability to handle the economy and defend US interests abroad, but he still lags other previous incoming presidents at the equivalent time.

Vice President-elect Mike Pence, however, said Trump has a mandate even as Democrats point out he lost the popular vote and question the legitimacy of his victory.

"Donald Trump won a landslide election," Pence said Sunday on CBS' "Face the Nation." "The American people spoke decisively, they wanted change and I promise ... come noon this coming Friday, change really begins and we are going to make America great again."

Starting from such a low base of approval gives Trump little leeway should things begin to go wrong in his administration. Presidents who get into trouble in the polls generally become less effective in molding public opinion in times of crisis and in exerting leverage on Capitol Hill.

It's also notable that while Trump took care to keep his supporters on his side during his post-election "thank you" tour, he's done almost nothing to reach out to the millions of Americans who view his inauguration with anxiety.

He has instead spent his transition waging personal vendettas on Twitter, castigating CNN and other media organizations while putting more credibility in the statements of Russia and Wikileaks founder Julian Assange than those of US intelligence agencies.

But if Trump proves skillful at handling the presidency, it's possible his approval rating could quickly rise. And for Trump's supporters, who sent him to Washington to fundamentally dismantle the political class, blasting Meryl Streep on Twitter, slamming journalists, defying the intelligence establishment and ignoring conventions on avoiding conflicts of interests is not troubling at all.

Future problems?

Still, the President-elect could be storing up future problems that could return and haunt him later in his administration.

Ethics lawyers have condemned his decision to flout the normal practice of presidents by not putting his assets in a blind trust as far short of what is necessary. Trump will hand over the running of his businesses to his sons, Eric and Donald Jr., and has pledged not to discuss them. But he will retain his financial stake, which means he can still boost his own wealth indirectly by decisions he will make as President.

The President-elect will also take office beset by looming political challenges in Congress.

Trump said at last week's news conference that Obamacare should be repealed and replaced nearly simultaneously , a sentiment that House Speaker Paul Ryan seemed to endorse at a CNN town hall. But no workable plan has emerged that could pass Congress and insure millions of people who will lose coverage if Obamacare is dismantled.

Senate Majority Leader Mitch McConnell is calling for a "stable transition period" between the two moving parts of building a new GOP health care plan and several Republican senators are anxious about moving too quickly.

Trump vs. his Cabinet

Disagreements are also brewing at the heart of Trump's own cabinet. While most of his nominees appear to be heading for confirmation, clear differences emerged between the President-elect and his national security team at their hearings on Russia, torture, the Iran nuclear deal and the need to preserve US alliances.

Their positions raised questions about how their conventional views would fit with a president who seems intent on disrupting foreign policy traditions. Trump tweeted on Friday that there was no reason to worry.

"All of my Cabinet nominee are looking good and doing a great job. I want them to be themselves and express their own thoughts, not mine!"

Traditionally, new presidents begin their administrations by using their inaugural address to call on the nation to unite after fractious political campaigns. Trump may do the same, though his scorched earth style leaves him with perhaps a bigger challenge in this area than any recent president. His handling of lingering questions about the extent of Russian interference in the election and the treatment of Hillary Clinton by the FBI could also be crucial to establishing credibility with those who oppose him.

For now, however, he remains hyper sensitive to the merest suggestion that his election victory was marred by outside influences, suggesting that corrosive questions about 2016 will linger long into his presidency

"What are Hillary Clinton's people complaining about with respect to the F.B.I. Based on the information they had she should never..... have been allowed to run — guilty as hell," Trump said in consecutive tweets on Friday.

Former Clinton spokesman Brian Fallon said on CNN last week that such comments bode ill for Trump's presidency.

"I think those tweets are just the latest indication that Donald Trump is someone very insecure in his victory," he said last week. "Every day, there are new developments and new shoes dropping, so to speak, that call into question the legitimacy of his win."