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In the fall of 2015, as the political world laughed at the idea that Donald Trump could win the White House, two Democratic operatives went on the attack.

They haven’t stopped since.

Throughout Mr. Trump’s unusual campaign and chaotic early presidency, as well as the impeachment proceedings and the coronavirus pandemic, Adrienne Watson and Nick Bauer have battled the president — first as part of the Clinton campaign and then, later, at the Democratic National Committee.

In the process, Ms. Watson and Mr. Bauer, along with a 35-person operation known as the party’s “war room,” have become a repository of Democratic opposition research on Mr. Trump — the operatives with the deepest knowledge of his weaknesses.

Now, as Democrats try again to defeat Mr. Trump, Ms. Watson and Mr. Bauer find themselves at the front of their party’s offensive charge.

At the direction of the Biden campaign, they’re expanding their effort and will become the central Democratic clearinghouse for attacking the incumbent president, a challenge Democrats last faced in 2004.

In recent weeks, Mr. Trump seems to be sustaining the most damage from self-inflicted wounds. But Ms. Watson warned Democrats not to count on Mr. Trump all-but-defeating himself, pointing to plenty of other moments — like the release of the Access Hollywood tape — when Mr. Trump surprised Democrats by his durability.

“The truth is that Trump has never imploded on his own,” she said. “This is going to be a tough fight, but we’re ready for it.”

The war room’s political slogan is simple: Trump first, America last.

In ads and messaging, the group portrays Mr. Trump as undone by his own narcissism, prioritizing his political interests and ego over the expertise that is needed to battle a deadly pandemic and lead a country.

The president has responded to all three ads the group has run, calling them “totally false advertising,” perhaps thinking they came from the Biden campaign.

There are plans to run more ads and to bring on operatives who have worked on primary campaigns, including Lily Adams, a key staff member on Senator Kamala Harris’s effort, Chris Hayden, from Senator Elizabeth Warren’s campaign, Sarah Peck, Danai Pointer and Eduardo Silva. Many of the war room staff members have been assigned to tracking Mr. Trump since 2016, amassing deep expertise in various aspects of his record and administration.

Typically, a “war room” is housed within a presidential campaign. The operations generally include plenty of public-facing political work — monitoring the media appearances of dozens of administration and campaign officials and firing off damaging quotes in news releases and on social media.

But much of the work happens just below the surface of politics. Operatives circulate information — often to reporters — that could appear in campaign ads and in debate questions, or tie up their opponent’s campaign in a hurtful media cycle.

During Hillary Clinton’s 2016 presidential campaign, the D.N.C. dispatched researchers to 40 states, pulled up 7,000 lawsuits involving Mr. Trump and developed a system that included 300 volunteer lawyers to review them. Ms. Watson pitched their findings to the news media.

What they found — from bankruptcies to sexual assault allegations — wasn’t enough to sway voters.

But as many Democrats mourned Mrs. Clinton’s defeat, the two operatives took their operation to the D.N.C. When Ms. Watson formally arrived at the committee on Jan. 2, 2016, she was greeted with a stack of files detailing harmful information about possible cabinet picks.

In the early months, she and Mr. Bauer spent a lot of time assessing why voters hadn’t seemed to care about opposition research that would have sunk another candidate.

They changed their approach, focusing early on the economy and health care, believing they would need to dismantle what the president saw as his biggest accomplishments. Rather than highlight Mr. Trump’s daily drumbeat of inflammatory remarks, Mr. Bauer and Ms. Watson devoted more time to the hurtful impacts of Mr. Trump’s presidency.

They also widened their scope, seeking to undermine senior administration officials around the president, believing that much of his credibility with voters stems from the trustworthiness of those he’s hired.

Biden staff members say the decision to run a key campaign operation out of the D.N.C. reflects the remote nature of campaigning during a pandemic, a desire to conserve campaign dollars and the expertise built up at the committee over the past four years.

“We’re proud and thrilled to have this extremely capable group led by Adrienne and Nick on our team, adding key firepower,” said Andrew Bates, Mr. Biden’s campaign spokesman.

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The NYT Politics live events are going digital. I’m helping to kick off the first of a four-part series on Thursday, with my fabulous colleagues Katie Glueck, Jennifer Medina, Annie Karni and Rachel Dry. We’ll be talking about political conventions — how they’re changing, why they matter and what it’s like to give a speech that can make or break your political career.

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A new 2020 election briefing

With nearly 16 weeks to go until the November general election, The Times is expanding its live coverage of the campaigns for president, the House and Senate, and governor, as well as coverage of voters, politics and policy across the nation.

Today we kicked off the inaugural post of our new briefing, a way to bring you, dear readers, all-day, all-live updates, news and analysis on the 2020 elections.

Here’s what you needed to know today:

• Mr. Trump faces a tough landscape as coronavirus cases continue to surge.

• Republican Party officials still plan to attend their convention in Florida, now an epicenter of the virus.

• Jeff Sessions, trailing in the Alabama polls, says his campaign is “electrified.”

• Texas Supreme Court rules against the State Republican Party holding an in-person convention.

• A new poll shows Mr. Biden leading in Texas.

• George Soros’s foundation is making a major donation toward racial justice efforts.

• California rejected more than 100,000 mail-in primary ballots, many of which election officials said arrived late.

… Seriously

In the words of 2020 presidential Democratic primary contender, Andrew Yang: Our dogs are not all right.

Dogs are becoming “overly bonded,” which means they’re intensely reliant on our presence to stay calm. Dogs signal this when they can no longer self-soothe and panic after an owner leaves a room or, God forbid, the house. It has to be addressed now — long before your dog is left home, solo, for long stretches when you return to the office — to avoid doggie meltdowns.

Just in case you needed one more thing to worry about.

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