On Thursday afternoon, President Trump claimed that he had won this week’s debate against former Vice President Joseph R. Biden Jr., then veered into complaining about how the Commission on Presidential Debates might change procedures for their next event to avoid him repeatedly talking over his opponent again.

“Why would I allow the debate commission to change the rules for the second and third debates when I easily won last time?” Mr. Trump tweeted, raising the prospect that he might not go ahead with their second scheduled debate.

A short time later, his political advisers devoted a 20-minute campaign call with reporters to denouncing commission members by name and accusing them of “bias.” The advisers insisted that Mr. Trump would take part in future debates, but the complaining hardly exuded confidence.

A day earlier, Mr. Trump was insisting, too, that he was being denied his due for his chaotic and widely panned debate performance. At a campaign rally that night in Duluth, Minn., he also complained that he had not received sufficient media coverage for nominations for the Nobel Peace Prize.

“We got nothing!” he told the crowd.

Over nearly four years in office, Mr. Trump has frequently changed his positions on issues, issued conflicting statements and shuffled through a revolving cast of staff.

The one constant has been the president portraying himself as a victim at every turn.

Be it congressional Democrats or Republican foes like the late Senator John McCain, the news media or the standards enforcers at Twitter, the impeachment inquiry or, now, the debate commission, Mr. Trump has repeatedly blamed others for problems and self-inflicted wounds, something he hopes will appeal to a shared sense of grievance among his supporters.

That instinct is now increasingly on display as he faces ominous polling showing him behind in his re-election campaign, a position that aides say is unfathomable for someone who has long staked his personal brand on “winning.” Mr. Trump, some advisers inside and outside the White House say, has telegraphed to them that he is scared of losing — and in particular, scared of losing to Mr. Biden, whom he does not respect.

Mr. Trump has taken to describing shadows on almost every wall: false claims that the election is “rigged” against him, complaints that the coronavirus pandemic was “unfair” to his record on the economy, insistence that people who disagree with him within his own government about policy matters are part of a concerted effort to undermine him.

He has lobbed accusations at Democrats who want more extensive public health measures, and who haven’t agreed to Republican terms on an aid package for people impacted by the coronavirus, usually saying they are trying to harm his re-election prospects.

ImageMr. Trump faces ominous polling showing him behind in his re-election campaign.
Credit…Erin Schaff/The New York Times

Even the personal troubles of Mr. Trump’s former campaign manager, Brad Parscale, whom the president has attacked in private for months and whom Mr. Trump demoted over the summer, became a vehicle for assigning blame. When Mr. Trump was told a few days ago that Mr. Parscale had been detained by the police for allegedly threatening to harm himself, the president ordered aides to write a statement blaming “Democrats” and “Republicans in name only” who had been critical of Mr. Parscale, according to two people familiar with what took place.

Claiming to be the victim of the political establishment has been key to Mr. Trump’s political persona since he entered the 2016 presidential race. And if he loses this time, he has spent months laying the groundwork for large swaths of voters to be receptive to his claim that it was wrongly taken from him.

Representative Peter King, Republican from Long Island, called Mr. Trump’s play for self-pity “a two-edged sword.” It has been successful in harnessing his base of voters who see him as fighting for them, but not necessarily with others whom he still needs to convince.

“I think it is important for the president to keep his base mobilized and tell some independent voters that the media is unfair to him,” he said. “But he can overplay that hand, so he has to watch it.”

Avoiding responsibility has been a trademark of the Trump White House on matters big and small, from the response to the coronavirus pandemic to Mr. Trump’s false claims about specific incidents of voting problems. As a businessman, too, Mr. Trump’s modus operandi was to deflect blame for anything that went wrong. But in a pandemic, when more than 200,000 people have died and millions have lost their jobs, Mr. Trump’s complaints about the system being unfair to him are discordant at best.

“The only way to convince people that you’re not a loser is to convince them that you’re a victim,” said Amanda Carpenter, a columnist for the Bulwark and a former communications director for Senator Ted Cruz. “Having something be rigged against him is the ultimate ego protector, because he never has to admit that he lost.”

But Mr. Trump’s habit of blaming others has done little to erase the forbidding polling reality he faces against Mr. Biden.

Both nationwide and in most crucial swing states, a slight majority of voters tend to disapprove of the job Mr. Trump is doing as president, as they have throughout most of his term in office. And it looks increasingly unlikely that voters will buy his argument that Mr. Biden presents a dangerous alternative.

Polls over the past week have shown Mr. Trump trailing Mr. Biden by anywhere from five to 10 points nationwide. And his fortunes are no better in many key swing states, including Wisconsin, Pennsylvania and Arizona: Recent polls from The New York Times and Siena College showed Mr. Biden with an eight to 10 point lead among likely voters in each of those three states. With one small exception, no credible survey this month has shown Mr. Trump ahead in any of them.

The president finds himself playing defense in every one of the states that he flipped four years ago, including in Iowa, where a Times/Siena poll this month gave Mr. Biden a three-point edge. Even in southern states that were key to his win in 2016, such as North Carolina and Florida, polls show him in a dogfight with Mr. Biden, hobbled — as he is elsewhere — by his stark unpopularity among women and his inability to maintain the confidence of suburban voters who had narrowly swung in his favor four years ago.


Credit…Ruth Fremson/The New York Times

His angry performance in the debate on Tuesday did little to quiet the concerns of such voters. A CNN snap poll conducted that night among registered voters found that by more than two-to-one, debate viewers thought Mr. Biden had been the winner.

And in a reminder of how unpopular his pugilistic, taunting style remains with most voters, respondents said by an equally wide margin — 67 to 32 percent — that the president’s attacks on Mr. Biden that night had been unfair.

The debate commission is expected to announce some changes soon to the format for the remaining two presidential debates. Whether Mr. Trump uses such changes as justification to skip his next debate, on Oct. 15, remains to be seen.

Scott Jennings, a Republican strategist, said that he is sympathetic to some of Mr. Trump’s complaints, particularly about his media coverage.

But he also described errors made by Mr. Trump that are followed by people rallying to his side, comforting him and then fighting for him — without the president ever acknowledging that he was the one who kicked off that kind of exhausting cycle.

“It’s statistically impossible for someone to be totally the victim 100 percent of the time,” Mr. Jennings said. “Sometimes you brought it on yourself.”

Giovanni Russonello contributed reporting.