The prevailing opinion inside the Trump campaign is that former Vice President Joseph R. Biden remains the most likely candidate to capture the Democratic nomination, and the campaign is plotting ways to sever Mr. Biden from the image of beloved former President Barack Obama.
Trump campaign officials said they expect Mr. Biden will survive the racial flap stirred up by Sen. Kamala D. Harris last week at the Democrats’ first 2020 primary debate in Miami. But the episode, they said, exposed an avenue of attack that could circumvent the aura of Mr. Obama that often protects his former right-hand man.
“Even though Biden took a big hit from Harris, the Trump campaign is operating under the assumption that he is still best positioned to be the nominee. That doesn’t mean they are not keeping an eye on Kamala and [Sen. Elizabeth] Warren, because they are,” said Republican Party strategist Ford O’Connell, who works closely with the White House.
The formula for going after Mr. Biden in a general election, he said, would be to aim for his six-term record as a senator from Delaware rather than his two terms in the White House alongside the country’s first black president.
“He’s got an Obama card he can play, but the problem is the 36 years of baggage before Obama. That’s the ticket in terms of getting him,” Mr. O’Connell said.
Ms. Harris used the same tactic in the debate to hit Mr. Biden for his opposition to federally mandated busing to desegregate public schools in the 1970s.
In a breakout moment in the debate, Ms. Harris, the daughter of a Jamaican father and Indian mother, mentioned Mr. Biden’s position on busing. She pressed Mr. Biden to apologize for his opposition and recalled the small role she played in desegregating schools in Berkeley, California.
“There was a little girl in California who was part of the second class to integrate her public schools, and she was bused to school every day — and that little girl was me,” she said. “So, I will tell you that on this subject, it cannot be an intellectual debate among Democrats. We have to take it seriously.”
Mr. Biden refused to apologize in the sharp exchange but fumbled to defend his record, which pulled down his poll numbers. Still, he has retained the front-runner position, albeit with less comfortable margins.
Mr. Biden also sits atop a powerful fundraising machine. His campaign announced Tuesday a $21.5 million haul in the roughly two months since he entered the race.
Ms. Harris’ rousing performance in the debate gave her campaign a burst of energy that propelled her into second place and within striking distance of Mr. Biden in several polls.
A faction inside President Trump’s campaign war room raised alarm that Ms. Harris is poised to dominate the black vote, a crucial bloc in Democratic primaries, and cut a path to the nomination similar to that of Mr. Obama in 2008. Mr. Obama began back in the pack while Hillary Clinton was the seemingly inevitable front-runner.
But the team has resisted shifting the focus in a major way from Mr. Biden, said a Trump campaign official.
“The opposition research is focused on Biden. And we hope we get Biden because when it comes to who’s got a better record, Trump has a significantly better record than Biden,” the official said, adding that the push to focus on Mr. Biden starts with Mr. Trump.
Mr. Biden is viewed as a unique threat to Mr. Trump because of the former vice president’s purported appeal among blue-collar voters in the Rust Belt who unexpectedly tilted the race to Mr. Trump in 2016.
What concerns the campaign the most about Mr. Biden are his close association with Mr. Obama and his promise of a “return to normalcy,” a slogan that builds on the news media’s relentless negative reporting about Mr. Trump, another campaign aide said.
“The return to normalcy is all about senior citizens and female voters that we lost in the 2018 midterm elections, folks who didn’t pull the lever for us or didn’t turn out,” the aide said.
That is why Team Trump is homing in on what it sees as significant weaknesses for Mr. Biden, including decades of Senate votes that don’t square with today’s political sensibilities and his flat-footed delivery on the stump and in debates.
Tim Murtaugh, communications director for the Trump reelection campaign, said the team isn’t excessively preoccupied with Mr. Biden.
“Joe Biden is an existential threat to Joe Biden. His poor performance on the campaign trail and lame defense of his four decades in public office have already caused him problems,” Mr. Murtaugh said.
“He was a bad candidate the first two times he ran for president, and there’s no reason to expect that he’s improved any. We are a year away from knowing who our opponent will be, and we are unconvinced that Joe Biden will be the nominee,” he said.
Mr. Murtaugh argued that Mr. Trump has a leg up on any of the two dozen other Democratic hopefuls, who have rushed to embrace far-left positions such as decriminalizing unauthorized border crossings, giving taxpayer-funded health care to illegal immigrants and axing private health insurance in favor of a government-run “Medicare for All” program.
“Regardless of the outcome of the Democrat primaries, President Trump is in as strong a position for reelection as any incumbent has ever been,” Mr. Murtaugh said. “His stellar record of success, including the growing economy and almost 6 million new jobs created, coupled with returning America to its leadership position on the world stage, will carry him to victory in 2020.”