President Trump is impugning former president Barack Obama, touting a conspiracy theory called “Obamagate” to rally his conservative base.

Joe Biden is embracing the 44th president, emphasizing their partnership as the presumptive Democratic nominee tries to consolidate support.

And Obama himself — after months of relative silence in the national political debate — has leveled sharp criticism at Trump’s handling of the novel coronavirus outbreak and is poised to take center stage this weekend when he addresses millions of young people in a virtual commencement address in prime time.

More than three years after leaving office, Obama figures to play a central role in the 2020 campaign with his former vice president likely to head the Democratic ticket. Biden has been in regular conversations with Obama, and Biden suggested in a Snapchat interview Wednesday that his former boss has been a sounding board as he deliberates over choosing his own running mate.

Soon, they will be more closely joining forces against Trump, who has obsessed with trying to overturn Obama’s legacy and has used him as a foil to blame for arguably self-inflicted political wounds — such as the Russia investigation and his management of the pandemic.

On Wednesday, as GOP allies ratcheted up their attacks on the Obama administration’s investigation of Russian influence, Trump tweeted an old video clip of Obama predicting on a late-night talk show that Trump would never become president. “Obama was always wrong!” he wrote.

“Trump’s fact-free fixation on Obama dating back to birtherism is so absurd and stupid that it would be comic if it wasn’t so tragic,” former Obama national security aide Ben Rhodes wrote in a tweet earlier this week.

The dynamics are taking shape as both sides scramble to reassess their strategies after the pandemic upended the campaign — halting rallies and in-person fundraisers, forcing a reassessment of the structure of the summer political conventions, and redrawing the expected fault lines in the contest.

Trump campaign spokesman Tim Murtaugh said in a statement that “the coronavirus criticism is meant to divert attention away from Joe Biden’s aimless campaign and disastrous record” and that Biden’s “oversight of the slowest economic recovery since World War II will be issues in the campaign, among other failings from his time as Obama’s vice president.”

Some former Obama aides have privately expressed frustration that he has not been more outspoken during Trump’s presidency, but he has told associates that his influence would wane with oversaturation, the aides said. Obama’s clout is essential for Biden, but his ability to help Democrats win elections was limited during his time in office, as shown by Democratic nominee Hillary Clinton’s loss to Trump in 2016.

Katie Hill, an Obama spokeswoman, said the 44th president “looks forward to campaigning aggressively this year for Biden” and other Democrats and emphasized that he believes “this election is too important for anyone to sit out.”

After weeks in which Trump played down the threat from the novel coronavirus, the president has sought to blame the Obama administration for leaving his own unprepared for the pandemic, falsely stating that it created new regulatory barriers that slowed the production of test kits.

Trump’s allies on Capitol Hill, including Sen. Majority Leader Mitch McConnell (R-Ky.), have suggested the Obama administration failed to develop a “game plan” for pandemics, when in fact it had produced a 69-page “playbook” of recommendations on how to deal with testing, funding personal protective equipment and emergency declarations.

Obama has not responded publicly to the criticism, but on a private 30-minute conference call Saturday with about 3,000 alumni of his administration, he slammed Trump’s leadership in the crisis as “an absolute chaotic disaster,” according to an audio recording obtained by Yahoo News.

During the call, in which Obama urged his network to support Biden, the 44th president also criticized the Justice Department’s decision last week to drop charges against Michael Flynn, who served as Trump’s first national security adviser, over making false statements to the FBI about his contact with Russian officials. The department seeks to overturn his 2017 guilty plea.

Senior political appointees determined that lower-level prosecutors and agents erred egregiously in the course of special counsel Robert S. Mueller III’s investigation of Russian interference in the 2016 election, prompting accusations they were bowing to pressure from the White House.

In his remarks, Obama called the move “the kind of stuff where you begin to get worried that . . . our basic understanding of the rule of law is at risk. And when you start moving in those directions, it can accelerate pretty quickly as we’ve seen in other places.”

His warning prompted McConnell to suggest that Obama should have “kept his mouth shut,” calling it “a little bit classless” for a former president to criticize a sitting one. On Sunday, Trump unleashed a series of tweets to amplify the “Obamagate” conspiracy that has taken root on the far right that falsely suggests Obama and Biden oversaw an effort to spy on Trump’s campaign to delegitimize his presidency.

Trump has called the alleged scandal “worse than Watergate” and has kept up a drumbeat of accusations that Obama committed a crime, though he declined to offer specifics when asked to explain the extraordinary charges during a Rose Garden news conference Monday. On Tuesday, Trump retweeted an image of Obama and Biden with the text: “These two orchestrated the most corrupt transition of power in United States history! Spies among us!”

“No one knows what Obamagate is, and that includes President Trump. It’s a hashtag in search of a scandal,” said Ned Price, a former CIA analyst who served as a National Security Council spokesman under Obama. “The only people it will galvanize are those already 1,000 percent behind” Trump.

On Wednesday, the clamor around the Flynn case intensified further as three Republican senators made public a recently declassified list of U.S. officials, including Biden, who purportedly sought to “unmask” Flynn’s identity in late 2016 and early 2017 — a common practice in the intelligence community but one that some conservatives have seized on to imply wrongdoing.

The list includes the names of more than three dozen former Obama administration officials. Among them are Biden, former White House chief of staff Denis McDonough, former FBI director James B. Comey, former CIA director John Brennan and former director of national intelligence James R. Clapper Jr.

The list was recently declassified by Trump’s top intelligence official, Richard Grenell, and given to the Justice Department as well as three Senate Republicans who then released it on Wednesday. Soon after, the president’s campaign blasted out an attack on Biden, questioning his role in the investigation into Flynn’s contacts with Russian officials -- raising the specter that the administration was essentially using the intelligence community to provide material for Trump’s re-election effort.

“It’s clear Biden is not being honest about what he knew about the targeting of Flynn,” read a statement from the campaign that was echoed by the president’s allies. Biden’s campaign called the issue an attempt by Trump and his supporters to distract from his handling of the pandemic.

The controversy over Flynn will likely only intensify in the days ahead. Late Wednesday, Flynn’s sentencing judge asked a former federal judge to oppose Justice’s request to dismiss the former Trump national security adviser’s guilty plea and examine whether Flynn should face a contempt hearing for perjury.

At the White House daily briefing Tuesday, press secretary Kayleigh McEnany read transcripts of congressional testimony from former Obama aides who said they did not see direct intelligence evidence of Trump’s campaign colluding with Russian operatives in 2016.

“Why then did we have many years of investigating collusion?” McEnany asked. “For three years, the American people were dragged through the mud and told that their choice for the president of the United States might have been a Russian asset based on no evidence at all.”

Steve Schmidt, a former Republican strategist who helped found a super PAC aimed at defeating Trump this fall, said Trump has tried to distract the public by returning to the “tangle of conspiracy theories that live in the fever swamps of Fox News and OAN and talk radio about the plot to undermine Trump. Grievance and conspiracy are the high-octane fuel of Trumpism, so Obama will play the role as the central person in this conspiracy.”

Some Obama alumni who participated in the conference call said they came away thinking that the former president made the remarks about Trump and the Flynn case with the expectation that they would be leaked publicly. A person close to Obama acknowledged that with thousands of people on the line, aides were aware that his remarks were likely to get out. That person spoke on the condition of anonymity to talk about a private event.

Yet aides cautioned that the call should not be interpreted as a starting gun for a more robust level of immediate campaigning by Obama. He is scheduled to deliver the virtual commencement address for high school seniors on Saturday that will air on the major television networks. But aides said he is not expected to mention Trump or Biden, focusing instead on how young people can get involved in their communities.

Obama’s and Biden’s teams are still coordinating over how they will campaign, a question that has been complicated by the coronavirus, which has confined both men to their homes in Washington and Delaware, respectively.

Obama aides pointed to his activities in the 2018 midterms as a road map for this fall. Obama began ramping up his campaigning for Democrats as the election neared, including an hour-long address in September at the University of Illinois at Urbana-Champaign in which he directly rebuked Trump and warned of “dangerous times.”

“President Obama is a force on the campaign trail — virtual or otherwise — and will be an enormous asset not just to our campaign, but to Democrats up and down the ballot,” said TJ Ducklo, a spokesman for the Biden campaign.

Biden aides hope to leverage Obama’s popularity, and large social media network, to drive their digital content, and they have discussed having Obama on Biden’s regular podcast.

It is clear that Obama is a much bigger online draw. The 146 videos that Biden’s campaign has put on YouTube this year have averaged about 28,000 views on the online video service, with few cracking above 100,000. Obama’s 12-minute video endorsing Biden last month racked up 1.9 million views.

Associates said that while they expect Obama to be critical of Trump, they do not expect him to focus solely on his successor. They pointed out that Biden will choose a vice presidential running mate who can play the role of regularly attacking Trump, freeing Obama to deliver a broader message.

“This is bigger than Trump — it’s who we are as a country,” said Jen Psaki, who served as White House communications director under Obama. “He’ll focus on his concerns before Trump about our move towards tribalism and division and less on attacking Trump as a human being. He’s more of a natural uplifter.”