WASHINGTON -- Investigations now entangle Donald Trump's White House, campaign, transition, inauguration, charity and business. For Trump, the political, the personal and the deeply personal are all under examination.

Less than two years into Trump's presidency, his business associates, political advisers and family members are being probed, along with the practices of his late father. On Friday, Interior Secretary Ryan Zinke became the fourth Cabinet member to leave under an ethical cloud, having sparked 17 investigations into his actions on the job, by one watchdog's count.

All of this with the first special counsel investigation against a president in 20 years hanging over Trump's head, spinning out charges and strong-arming guilty pleas from underlings while keeping in suspense whether the president -- "Individual 1" in prosecutor Robert Mueller's coded legalese -- will end up accused of criminal behaviour himself.

The scope of the scrutiny has shaped Trump's presidency, proving a steady distraction from his governing agenda. So far, much of it has been launched by federal prosecutors and government watchdogs that eschew partisanship. The intensity is certain to increase next year when Democrats assume control of the House and the subpoena power that comes with it.

Although Trump dismisses the investigations as politically motivated "witch hunts," his high-octane Twitter account frequently betrays just how consumed he is by the scrutiny. He's also said to watch hours of television coverage on milestone days in the investigations.

"It saps your energy, diverts your attention and you simply can't lead because your opponents are up in arms against you," Cal Jillson, a Southern Methodist University political scientist and historian, said of the scrutiny. "It weakens your friends and emboldens your enemies."

Almost midway through his term, Trump is struggling to deliver on his central campaign promises. He may end the year without a Republican-led Congress giving him the $5 billion he wants for a border wall. And he's previewed few legislative priorities for 2019.

Even if he had, it's unlikely the new Democratic House majority would have much incentive to help a president weakened by investigations rack up wins as his own re-election campaign approaches.

Perhaps not since Bill Clinton felt hounded by a "vast right-wing conspiracy," as Hillary Clinton put it, has a president been under such duress from investigation.

This jeopardy has come with Trump's party in control of Congress and the Justice Department driving at least three separate criminal investigations. They are the Mueller probe looking into possible collusion, obstruction of justice or other wrongdoing in contacts between the Trump campaign and Russia; the New York campaign-finance case involving hush money paid to Trump's alleged lovers; and now a case from New York, first reported by The Wall Street Journal this past week, examining the finances and operations of Trump's inaugural committee and whether foreign interests made illegal payments to it.

Behind those matters is a battery of lawsuits or inquiries from state attorneys general and other parties tied mainly to Trump businesses.

At best, the investigations are overshadowing what has been positive economic news. At worst, the probes are a threat to the presidency, Trump's family and his business interests.

The deep diving will only grow in the new year when Democrats take over the House. They are expected to launch their own investigations and could pursue impeachment, though party leaders caution they could face a political backlash by taking that step.

Even if Trump avoids impeachment, the Democratic investigations will create headaches. Administration officials will be called to testify before Congress and lawmakers will seek a trove of documents, probably including Trump's tax returns, which he has refused to make public.

A bare-bones White House staff may struggle to keep up. A tally by the Brookings Institution finds more than 60 per cent of Trump's top aides have left in the first two years, a turnover rate exceeding the previous five presidents. In addition, 10 Cabinet secretaries have departed, more than Barack Obama, George W. Bush and Clinton lost in two years. The shake-ups now have left Mick Mulvaney, Trump's budget chief, doing double duty indefinitely as the president's chief of staff.

That combination makes it hard to imagine a president effectively engaged in policy, even if -- as in the case of Clinton -- the drawn-out investigations lead to an impeachment that fails to remove the president.

"The modern presidency is extraordinarily complex and demanding so you need the president's full attention," Jillson says. "Where your attention should be, you're also thinking about meeting with your lawyers."

As the investigations mount, few Republicans have dissociated themselves publicly from Trump. But privately, some lawmakers do worry that the investigations will damage his re-election prospects and their own chances in 2020 House and Senate races.

The federal campaign finance probe has put GOP lawmakers in a particularly awkward position. Prosecutors -- as well as Trump's longtime personal lawyer Michael Cohen and a tabloid company that has long been an ally -- assert that Trump directed hush payments to keep women quiet about alleged affairs in the closing weeks of the 2016 campaign. Such a payment would violate campaign finance laws. Cohen was sentenced this past week to three years in prison.

Underscoring the balancing act for Republicans, outgoing Sen. Orrin Hatch of Utah initially stated that he didn't much care about Trump being implicated in Cohen's crime, then thought better of his words.

"I made comments about allegations against the president that were irresponsible and a poor reflection on my lengthy record of dedication to the rule of law," Hatch said in a statement Friday.

Five people in Trump's orbit have pleaded guilty to charges in the continuing Mueller probe. Among them, Paul Manafort and Rick Gates were Nos. 1 and 2, respectively, for a time in Trump's presidential campaign. George Papadopoulos, a lower-level campaign adviser, was sentenced to 14 days in prison and is out. The others are Michael Flynn, who was Trump's first national security adviser in office and is to be sentenced Tuesday, and Cohen, who is expected to begin his sentence in March.

In addition, the special counsel's office says Flynn, in giving 19 interviews and turning over a mountain of documents, has assisted in a criminal investigation that has yet to be revealed.

In other words, there's no end in sight.

Trump is also exposed to legal peril beyond that from federal prosecutors. Among the lawsuits or investigations:

Democratic attorneys general in Maryland and the District of Columbia and congressional Democrats are challenging the Trump Organization's business transactions with foreign and state government interests, such as those at his Washington hotel, citing the constitutional ban on presidents taking payments from such sources without congressional consent.

Summer Zervos, once a contestant on Trump's TV show, has sued Trump for defamation for accusing her of lying. She alleged in 2016 that he made unwelcome physical contact with her. He's failed several times to derail the case.

New York tax officials are looking into whether Trump or his charitable foundation misrepresented tax liability. In addition, the New York tax department said it is "vigorously pursuing all appropriate avenues of investigation" after a New York Times report found Trump and his family, going back to transactions by his father, Fred Trump, cheated on taxes for decades. The report said Trump received the equivalent today of at least $413 million from his father, much of it through dubious tax manoeuvrs. Trump called the report "a very old, boring and often told hit piece on me."

New York authorities allege in a lawsuit that Trump illegally tapped his charitable Trump Foundation to settle legal disputes, help his campaign for president and cover personal and business expenses, including the purchase of a life-size portrait of himself for $10,000.

Stanley Renshon, political scientist at the City University of New York and a psychoanalyst, says all of that adds up to a lot of people, not just the left, "trying to make his presidency untenable."

It is, perhaps, vaster than the right-wing "conspiracy" the Clintons endured, Renshon says. "I call it the everybody conspiracy."