WASHINGTON • It has been a particularly bad week for Mr Donald Trump, with his unfavourability ratings spiking again, reports of a new Republican effort to deny him the nomination for the presidency at the party convention next month and details emerging of his cosy ties with President Vladimir Putin and Russian businessmen.

Last week began on a sour note for the real estate mogul turned politician after his anti-Muslim comments in the aftermath of the Orlando massacre - which left 49 people dead - were slammed by President Barack Obama and Mrs Hillary Clinton, his presumptive Democratic opponent in November.

Even House Speaker Paul Ryan, the highest-ranking elected Republican, dismissed Mr Trump's proposed ban on Muslim immigrants as not in the country's interest.

Then polls showed Mr Trump slumping in the polls again and, in what appeared to be even more alarming for him, the political news website, Politico, said he was setting modern records for political toxicity.

Seventy per cent of Americans surveyed in an ABC News/ Washington Post poll had an unfavourable opinion of the real estate tycoon, up 10 points over the past month. His favourable rating cratered at 29 per cent, down from 37 per cent last month. His favourability rating in a Bloomberg Politics poll was just 31 per cent, with 66 per cent viewing him unfavourably.

But Politico noted that the intensity of the antipathy towards Mr Trump and the lack of enthusiasm for him was unprecedented.

In the ABC News/Washington Post poll, 56 per cent of respondents had a "strongly unfavourable" opinion of him, compared to just 15 per cent who had a "strongly favourable" opinion. In the Bloomberg poll, 51 per cent had a "very unfavourable" opinion of him, with only 11 per cent having a "very favourable" opinion.

Voters with a strongly unfavourable opinion are "obviously more difficult to move than people who are undecided or just unfavourable", Quinnipiac University pollster Peter Brown was quoted as saying.

But The Washington Post, in an opinion piece on Friday, said Mr Trump might not even be capable of acknowledging what's happening right now.

It referred to a rally in Dallas on Thursday where Mr Trump said: "When I poll, I do fine, but when I run I do much better... it's like an amazing effect."

The newspaper also carried a separate report on Mr Trump's relationship with Mr Putin and his warm views towards Russia, calling them "among the more curious aspects of his presidential bid".

The newspaper noted that Mr Trump has called for a new partnership with Moscow and has surrounded himself with a team of advisers who have had financial ties to Russia.

Since the 1980s, Mr Trump and his family members have made numerous trips to Moscow in search of business opportunities, and they have relied on Russian investors to buy their properties around the world, according to the newspaper.

"The dynamic illustrates the extent to which Trump's worldview has been formed through the lens of commerce rather than the think- tanks, government deliberations and international diplomatic conferences that typically shape the foreign policy positions of presidential candidates," it added.

Upset with The Washington Post's coverage on him, Mr Trump decided last week that he would no longer issue press credentials to journalists from the newspaper and would stop them from covering his campaign events.

Meanwhile, some Republican delegates - furious at his continued fumbling and splits with conservatives - are trying to change party rules in meetings a week ahead of July's convention, according to press reports.

"This literally is an 'Anybody but Trump' movement," said Colorado delegate Kendal Unruh, who is leading the anti-Trump effort.