Historians may one day conclude that the extraordinary 2016 US election was decided in early August when Donald Trump suffered one of the most politically calamitous weeks ever to befall a presidential nominee.

Trump's devastating wounds were mostly self-inflicted and arose from a series of gaffes, petty feuds, and xenophobic comments that left even some of his own supporters wondering if it was too late to replace him.

It began when the billionaire picked a fight with the parents of Captain Humayun Khan, a Muslim US soldier who died a hero in Iraq in 2004 at the hands of a suicide bomber.

Khizr Khan, his father, had spoken at the Democratic Convention at the end of July, lambasting Trump over his proposal to ban Muslims from entering the US. Trump could not let it pass and in response, on national television, he implied that Khan's wife Ghazala had not been allowed to speak publicly because of the couple's Muslim faith. Those and subsequent comments sparked outrage across American society and in the military, one of Trump's own core constituencies. Republican leaders begged him to apologise but he would not.

Advertisement

Perhaps even more damaging was Trump's refusal for several days to endorse Paul Ryan, the most senior Republican official, who is seeking re-election to Congress. Trump, apparently motivated by a personal feud, sparked a near civil war in his own party. His own running-mate Mike Pence contradicted him and endorsed Ryan. Reince Priebus, chairman of the party, attempted to recruit Trump's children to stage an "intervention" to change his mind.

He sparked negative headlines telling a mother with a crying infant at one of his rallies to "get the baby out of here". He had initially encouraged the infant and his mother to stay despite the loud crying, before saying with a smile that "I was only kidding" . The Washington Post later concluded, based on reporting by a journalist sitting behind the mother and baby and the mother herself, that Trump was "unfairly maligned here". The mother made her own decision to briefly leave to calm the baby and they returned.

Trump made gaffes that included not knowing Russia had taken the Crimean Peninsula two years ago. He savaged Japan, suggesting if the US was attacked, the Japanese would "sit home and watch Sony television". A former ally also alleged Trump had asked three times in a foreign policy briefing why he couldn't use nuclear weapons as president. When asked which women he would put in the Cabinet, the businessman could name only one, his daughter Ivanka.

Abandoning traditional decorum, President Barack Obama launched a five-minute diatribe in the White House East Room, calling the property mogul "unfit and woefully unprepared" for office.

Michael Morell, former acting head of the CIA, called him an "unwitting agent" of Vladimir Putin because of his pro-Russian policies.

Joe Scarborough, a former Republican Congressman turned talk show host, said he had received many calls about the billionaire's mental health. Karen Bass, a Democratic Congresswoman, launched an online petition calling for Trump to undergo a mental health evaluation to judge if he is "mentally fit to lead the free world", suggesting he may have Narcissistic Personality Disorder.

Trump responded to attacks on his state of mind. He told a rally in Wisconsin it was Clinton who was "pretty close to unhinged" and an "unbalanced person".

Polls at the end of his terrible week showed Trump sinking to a perhaps insurmountable deficit against Clinton. Suggestions emerged that Trump's advisers had no control over him; campaign staff were said to feel they were "wasting their time" and their mood was described in one leak as "suicidal".

Paul Manafort, Trump's campaign chief, denied such reports but pointedly said "the candidate is in control of his campaign". Behind the scenes, the campaign was described as "Crazytown".

The fear for Republicans was that Trump's growing unpopularity could have a knock-on effect on other races in November, leading the party to lose control of the Senate. Party insiders were exploring what the contingency would be if Trump left the fray. At the weekend, Trump attempted to turn the corner, publicly endorsing Ryan in his re-election race and calling him a "good man".

Polls: how is Trump rating?

1. RealClearPolitics.com yesterday gave Hillary Clinton an average national poll lead of 6.9. She has a 16.7 higher favourable rating than Donald Trump. The betting odds favour her by 76 to 24.

2. Of seven polls from IBD/TIPP, NBC/WSJ, McClatchy, Reuters, LA Times, Fox and ABC/WP in the past few days, Clinton is ahead nationally by between 7-15 per cent in five and by 1-4 per cent in two.

3. In Florida, Clinton is ahead by 6 in a Suffock University poll.

4. Two separate polls of Michigan have Clinton up by 9 and 10.

5. Clinton is ahead in RCP's list of battleground state poll averages except for Georgia and Missouri. She has healthy leads in Pennsylvania, Wisconsin, New Hampshire, Colorado and Virginia.

6. A poll of Republican-leaning Georgia shows her ahead by 4.

7. Polls show Barack Obama's job approval generally above 50 per cent.

8. The one bright spot for Trump is polling on whether the US is on the right or wrong track. Three polls put the wrong track ahead by 25, 30 and 4.