President Trump, already the most media-accessible president in memory, is talking to journalists almost nonstop as his successes pile up ahead of the midterm elections.

Take Tuesday, for example.

Mr. Trump opened an Oval Office meeting to the press in late morning to accept the resignation of Nikki Haley as ambassador to the United Nations. Such a high-profile departure ordinarily wouldn’t be a positive for the White House, but the president and Mrs. Haley made clear that the separation was friendly. They took questions from journalists for 20 minutes on a variety of subjects.

“Anything else?” the president asked when reporters seemed to be running out of questions.

Veteran journalists can’t remember anything like it.

“In my experience covering White Houses, from Reagan to George W. Bush, we’ve never had that kind of access from a president before,” said Richard Benedetto, a retired White House correspondent who teaches at American University. “He doesn’t get credit for being so accessible. He answers questions all over the place.”

Impromptu give-and-take sessions with the press are rare for most presidents. But Mr. Trump prides himself on being an unconventional president.

His meeting with Mrs. Haley ended around 11 a.m., and he was just getting started.

As Mr. Trump departed the White House for a campaign rally in Iowa on Tuesday afternoon, he stopped on the South Lawn to take more questions from reporters, as he often does. Over the roar of Marine One’s engines, Mr. Trump took another 37 questions in about 15 minutes, including some regarding Mrs. Haley’s possible replacement and his relationship with Deputy Attorney General Rod Rosenstein.

He still wasn’t finished.

Told that a writer for New York magazine was interviewing White House aides for an article on the job status of Chief of Staff John F. Kelly, Mr. Trump granted the writer, Olivia Nuzzi, an impromptu personal press conference in the Oval Office with Mr. Kelly, Secretary of State Mike Pompeo and Vice President Mike Pence.

Aboard Air Force One later on the flight to Iowa, Mr. Trump invited the press “pool” of reporters to his cabin for an off-the-record discussion for 33 minutes. These invitations from presidents in the past were extremely rare, but Mr. Trump has held at least two in-flight sessions with reporters in his airborne office this year.

The White House agreed to put some of the president’s answers on the record, on topics including China, North Korea and U.S. ethanol policy.

On Wednesday, during a briefing on Hurricane Michael, the president kept reporters in the Oval Office for another 23 minutes. “He’s on a roll,” observed one veteran White House journalist.

Although Mr. Trump has been more available to the media than other presidents since the start of his term, he has been engaging with the press even more frequently in recent weeks. He has had many positive developments to discuss, including historically low unemployment rates, a new trade deal with Mexico and Canada, and the confirmation of Supreme Court Justice Brett M. Kavanaugh.

At the same time, the White House is holding fewer press briefings.

“The president is always the best spokesperson for his administration,” White House press secretary Sarah Huckabee Sanders told The Washington Times. “Any time the American people get to hear directly from him, it is a good thing.”

One TV correspondent who covers the White House sees “a conscious strategy here to be more available.”

“The White House knows that all of his comments drive news cycles, so the more you can step up the metabolism of the news cycle, the better it is for him,” said the reporter, who spoke on the condition of anonymity. “Also, I think he loves the attention. He has strongly held opinions, and he needs to tell people about them.”

Then there are the campaign rallies, where Mr. Trump takes his case directly to supporters. He is holding as many as four rallies per week this month and is speaking for more than an hour at locations such as Johnson City, Tennessee, and Council Bluffs, Iowa.

Mr. Trump’s departures on Marine One from the South Lawn have become a staple of his dealings with the press, and he controls the interactions completely. If the president is hit with unpleasant news such as the Russia investigation, then he can simply walk straight to the helicopter and avoid questions. If he has positive news to discuss, such as the Kavanaugh confirmation or strong economic numbers, then he can approach the assembled media.

And he can walk away to his noisy chopper whenever he wants.

“It’s all him,” the TV reporter said. “The format is the ultimate home-court advantage. All the network reporters are lined up behind a chain begging for his attention, and he can pick and choose who he favors and who he doesn’t favor. He loves it, and it works for him.”

Mr. Benedetto said the media shouldn’t complain about the dwindling number of press briefings by Mrs. Sanders, given the unprecedented level of direct presidential access.

“If you’re a reporter, you want to know what the president is thinking every day,” Mr. Benedetto said. “You don’t often get that from the daily briefing. When you get the words directly from the president on a daily basis on every issue that comes along, that should be paradise for a reporter who is covering the White House. It matters not whether you like where he stands or don’t like where he stands. The fact is, we want to know where he stands. And that’s what we’re getting.”

White House aides also augment the president’s weekly agenda with a variety of so-called background briefings with reporters, usually on conference calls. The aides almost always insist on anonymity to conduct those briefings — a long-standing custom under numerous administrations.

Mr. Benedetto said Mr. Trump’s interactions with the media are vastly different from those of his predecessor.

“It’s just the antithesis of Barack Obama,” he said. “Obama was very careful in expressing his views on anything that came along that was slightly controversial. He tested the waters by having his secretary of state do it, or having his press secretary do it, or having his vice president do it. He used them as kind of a shield before he actually came out.”

Mr. Benedetto recalled an episode in 2012 when Mr. Obama reversed his position and came out in support of same-sex marriage after Vice President Joseph R. Biden did.

“He let Joe Biden come out and claimed Biden spilled the beans,” Mr. Benedetto said. “That wasn’t Biden spilling the beans. That was Biden being a stalking horse. It was an example of how well-managed they were, compared with how wide open the Trump administration is.”

The president’s high level of engagement with the press is especially striking in light of his frequent attacks on the “fake news” and his criticism of the media as “the enemy of the people.”

“He loves to talk to reporters,” the TV correspondent said. “The media is the metric for him that judges his presidency, and he loves to engage. He’s trying to ‘work the refs’ a little bit, and that’s standard presidential behavior.”

The challenge for the White House was underscored by the latest report from the conservative Media Research Center. Its analysis of network news coverage over the summer found that 92 percent of the news stories about Mr. Trump were negative.

The group called it “the most hostile coverage of a president in TV news history.”

On Wednesday afternoon, a media horde assembled on the South Lawn of the White House. Dozens of journalists were hoping the president would stop to talk on his way to a campaign rally in Pennsylvania.

At the appointed time, Mr. Trump emerged from the Oval Office.

For once, he walked straight to his helicopter and just waved to the press.