WASHINGTON >> In theory, President Donald Trump summoned television cameras to the heat-baked Rose Garden early Tuesday evening to announce new measures against China to punish it for its oppression of Hong Kong. But that did not last long.

What followed instead was an hour of presidential stream of consciousness as Trump drifted seemingly at random from one topic to another, often in the same run-on sentence. Even for a president who rarely sticks to the script and wanders from thought to thought, it was one of the most rambling performances of his presidency.

He weighed in on China and the coronavirus and the Paris climate change accord and crumbling highways. And then China again and military spending and then China again and then the coronavirus again. And the economy and energy taxes and trade with Europe and illegal immigration and his friendship with Mexico’s president. And the coronavirus again and then immigration again and crime in Chicago and the death penalty and back to climate change and education and historical statues. And more.

“We could go on for days,” he said at one point, and it sounded plausible.

At times, it was hard to understand what he meant. He seemed to suggest that his presumptive Democratic challenger, former Vice President Joe Biden, would get rid of windows if elected and later said that Biden would “abolish the suburbs.” He complained that Biden had “gone so far right.” (He meant left.)

Even for those who follow Trump regularly and understand his shorthand, it became challenging to follow his train of thought.

The appearance came on the same day that the president’s estranged niece, Mary L. Trump, a clinical psychologist, published a book questioning his mental health and asserting that pathologies stemming from his childhood are playing out now on the world stage. Trump has not commented about the book, but in the past he has described himself as “a very stable genius.”

The focus of the evening session with reporters took a turn after Biden received extensive television coverage for his $2 trillion climate plan earlier in the day, according to a senior official who spoke on the condition of anonymity. The Hong Kong Autonomy Act, the ostensible reason for his appearance, was treated as an afterthought.

In effect, though, the news conference turned into a campaign speech to substitute for the one Trump was scheduled to give last weekend in New Hampshire only to cancel amid concerns about flagging attendance, citing a possible storm at the site of the rally. While presidents as a general rule are not supposed to engage in overt campaigning from the White House itself, Trump made little effort to disguise his intent as he mentioned Biden’s name more than 20 times.

The appearance came on a day when Trump seemed eager to challenge convention and, at times, basic facts. During an earlier interview with CBS News, he denied that Black Americans suffered from police brutality more than white Americans.

Asked why Black Americans were “still dying at the hands of law enforcement in this country,” Trump said: “So are white people. So are white people. What a terrible question to ask. So are white people. More white people, by the way. More white people.”

Statistics show that while more white Americans are killed by the police overall, people of color are killed at higher rates when accounting for population differences. A federal study that examined lethal force used by the police from 2009 to 2012 found that a majority of victims were white, but Black people were 2.8 times likelier to be killed than white people.

In the same interview, Trump dismissed concerns about the Confederate battle flag. “With me, it’s freedom of speech. Very simple. Like it, don’t like it, it’s freedom of speech.”

Asked about those who see it as a painful symbol of slavery, he said: “I know people that like the Confederate flag and they’re not thinking about slavery.”

In a separate interview with the conservative website Townhall.com published on Tuesday, Trump falsely claimed that a white couple in St. Louis who confronted peaceful marchers outside their home with guns were on the verge of being attacked. “They were going to be beat up badly, and the house was going to be totally ransacked and probably burned down,” he said.

Video of the episode showed that the protesters at no point physically threatened the couple.

While advertised as a news conference, in fact the president took only a few questions, devoting six minutes of the 63-minute event to responding before abruptly cutting it off. But he promised he was not finished: “We will be having these conferences again.”

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