There was sunshine, palm trees and the endless expanse of ocean. There was golf with Jack Nicklaus, the most successful player of all time. There was a dinner that included stone crab, oysters, jumbo shrimp and clams; turkey, beef tenderloin, lamb and salmon; Chilean sea bass, red snapper and braised short ribs.

'America's straightest arrow': Robert Mueller silent as urgency mounts Read more

But as Donald Trump spent Thanksgiving at his opulent Mar-a-Lago estate – or “the southern White House”, as he called it in a teleconference with the military – there was something else on the menu: self-congratulation, grievance and paranoia. The 72-year-old was being confronted by a glimpse of what life might look if the electorate forces him into early retirement. One long game of golf in the Florida sun.

Trump is approaching the midway point in his presidency and, some argue, a point of no return. The recent midterm elections left him wounded, House Democrats are said to be aiming a “subpoena cannon” at every aspect of his life and special counsel Robert Mueller’s Russia investigation appears to be nearing its endgame.

“There’s no doubt we’re entering new territory and Donald Trump is in big trouble,” said Larry Jacobs, the director of the Center for the Study of Politics and Governance at the University of Minnesota. “The election results, no matter what he says, were devastating to him. The coalition he put together is clearly strained and he seems incapable of creating consensus.”

Just shut the hell up and get on the helicopter. Give us a rest from your crazy Michael Steele, former RNC chair

Just over a month ago, the landscape looked very different. Trump celebrated the confirmation of his second supreme court justice, a trade deal with Canada and Mexico, the release of an American pastor from prison in Turkey and the lowest unemployment rate for nearly half a century. He was chatting regularly to the media and had rapper Kanye West over to join in the fun. Newt Gingrich, the former House speaker, confidently predicted to the Guardian: “Unless something terrible happens to the economy, he’ll be re-elected.”

But on 6 November, the American people delivered a reality check. Republicans held the Senate but as the final House results trickle in, Democrats lead by more than 8.6m votes: 53.1% to 45.2%. The party has a net gain of nearly 40 seats, its biggest sweep since Watergate. Ominously, they won in rust belt states that were pivotal to Trump’s victory in 2016.

In response, the president has been acting like a man cornered. The catalogue is too long to list in full but here are some of the lowlights:

Trump fired Jeff Sessions and hired Matthew Whitaker as acting attorney general, in what many see as a threat to the special counsel.

He tried to ban a CNN correspondent from the White House but lost in court.

He skipped a visit to a military cemetery in France.

He criticised the admiral who oversaw the raid that killed Osama bin Laden.

He floated bizarre theories for the wildfires in California, twice referred to the destroyed city of Paradise as “Pleasure” and revelled in ignorance of climate change.

He referred to the Democrat Adam Schiff as “Adam Schitt”.

He issued a bewildering statement (633 words with eight exclamation marks) questioning the CIA’s reported conclusion that Saudi crown prince Mohammed bin Salman was responsible for the death of Washington Post columnist Jamal Khashoggi.

His daughter Ivanka was caught using a personal email account for government business.

He scolded the ninth circuit court of appeals, earning a rare rebuke from the chief justice of the supreme court.

It was reported that he wanted the justice department to prosecute Hillary Clinton and former FBI director James Comey.

He authorised troops on the US-Mexico border to use “lethal force”, despite concerns their presence is a political stunt.

And another thing: the stock market tanked, raising fears of economic slowdown.

It all became so much that on Wednesday, Michael Steele, the former chairman of the Republican National Committee, tweeted that Trump should “just shut the hell up and get on the helicopter. Give us a rest from your crazy. You don’t know the 9th circuit from a circuit breaker. It’s Thanksgiving for crying out loud. Let us be thankful for your silence. You’ve said enough this week.”

‘There is no learning curve’

Trump’s inability to stay silent suggests he has learned nothing from his election drubbing. Other presidents have suffered similar fates in the midterms, only to bounce back and win re-election. But they have done so by making changes and showing humility; when Trump was asked by Fox News to rank himself in the pantheon of great presidents, he awarded himself an A+; when he was asked by a reporter what he was grateful for on Thanksgiving, he talked about himself.

Play Video 0:47 Donald Trump says he's thankful for himself at Thanksgiving – video

Jacobs said: “Disaster has hit the Republican party and everyone but Trump recognises that. When Ronald Reagan got hammered in 1982, there was a major repositioning and he won in a landslide in 1984. When Bill Clinton, George W Bush and Barack Obama got hammered in the midterms, there were course corrections. There is no learning curve with Donald Trump. He has shown he is unable to respond to this reality.”

If Trump is cornered, the judges he disdains may finally bring him down | Walter Shapiro Read more

The situation is only likely to darken, Jacobs predicted. “Obviously with the investigations starting soon in the House, Trump and Republicans will be able to tarnish Democrats as obstructionist, but if Democrats manage to reveal corruption, it’s going to damage Trump’s claim to drain to swamp. He’s going to look swampy.

“This is an entirely different scenario heading into 2019: the analogy is trench warfare in world war one. The bigger problem across the country is there are not enough Republicans and clearly Trump is motivating young people and independents in ways we have not seen before. He is very good at mobilising the base but the Republican base is not enough to save him in the presidential election.”

Although Trump seems to have conquered the Republican party, Jacobs believes its members will read the runes, especially the Senate majority leader, Mitch McConnell, noted for his ruthlessness. Jeff Flake, the retiring senator from Arizona, has called for Trump to face a primary challenge.

If Trump lets the media and Democrats draw him into a negative constant fight over trivia, the election will be close Newt Gingrich

Jacobs said: “I see it getting worse on all these fronts in 2020. Is it inconceivable that [outgoing United Nations ambassador] Nikki Haley would explore a run? I think the conversation is going to move in that direction.”

It has long been speculated that Trump has something to hide: his tax returns, his business dealings, his peculiar devotion to autocrats. Now all are about to be put under the microscope by Schiff and others.

There are also signs that Mueller’s investigation could be reaching a critical phase, with Trump having submitted written answers and reports that a fresh set of indictments centred around WikiLeaks and Roger Stone is imminent. Just because Trump is paranoid doesn’t mean that they aren’t out to get him.

Rick Tyler, a political analyst and Republican consultant, said: “Donald Trump seems like he’s worried about two things. First, he’s clearly worried about the Mueller report. If it was purely a question of ego and whether Russia helped him get elected, this is an overreaction. There’s something else going on.

“Second, if you analyse Saudi Arabia and the Khashoggi incident, what Trump says makes no sense. Saudi Arabia is not going to cancel contracts and only has a negligible impact on the cost of oil and gas. Yet Trump promoted the awful cover story. He’s hiding something. There’s something there. He’s not protecting the crown prince; he’s protecting himself.”

Facebook Twitter Pinterest Protests in New York City on 8 November called to protect the Mueller investigation. Photograph: Michael Nigro/SOPA Images/REX/Shutterstock

‘He has real talents’

According to Gallup, Trump is the only president in the modern era whose job approval ratings have never been above 50%. Tyler said. “Say what you like about Donald Trump, he has real talents. But he has misused those talents. He could have struck a deal on a big infrastructure package, for example. But he retreated to his base, which only has the potential of shrinking. He keeps the base together by keeping them angry and humans can only stay angry for so long.”

Trump’s staunchest supporters are unmoved. Gingrich said via email: “Reagan was at 35% approval in January 1983. If President Trump goes to a base-broadening strategy, leaving the Democrats to flounder in negativity and fantasy policy ideas, he will win handily. If Trump lets the media and Democrats draw him into a negative constant fight over trivia, the election will be close.”

US media must 'get smarter' to tackle Trump, says Hillary Clinton Read more

Sebastian Gorka, a Fox News analyst and former deputy assistant to Trump, described claims that the president is in a downward spiral as “wishful thinking” and predicted victory in 2020. “Cake walk,” he wrote in a series of text messages. “With liars and loonies like Schiff and Crazy Maxine [Waters] running committees?? Even Dem voters will be driven crazy.”

Perhaps. But Democrats are spoiling for a fight. Kurt Bardella, a political columnist and former congressional spokesman, said: “We’re going to see for the first time in his presidency some substantive pushback from Congress. Democrats will no longer be passively commentating; they will be able to take tangible steps to find out what’s going on in this administration.

“Starting in January, Congress has the tools and mechanisms to push more and do more than be outraged. They can hold hearings, get documents, compel testimony. They can get access to the people around the White House and see what they think is going on: are people raising the alarm?

“I don’t think Trump fully understands how comprehensive the tools of oversight are for Congress because he’s never had to deal with it. These tentacles go far deeper and far broader than he can know. We’re going to see an entirely different level of paranoia with the president testing the limits of executive power unlike any president before as the walls close in.”