CNN  — 

Barack Obama held back his most biting critiques of President Donald Trump in the first years of his post-presidency, hoping the lack of constant attacks would make his voice even more powerful at a time he thought it was most needed.

That time, Obama believes, is now.

The former president, according to people close to him, sees his years of holding back on Trump as key to his ability to forcefully attack his successor on behalf of Joe Biden, his former running mate and the man running to unseat a President who has made sullying Obama’s legacy central to his political rise.

Obama is now joyfully castigating Trump on behalf of Biden, both laying out his policy differences with his successor and leveling biting indictments of some of Trump’s personal obsessions. Obama is paying close attention to Trump’s day-to-day actions and has begun to work those critiques into his speeches, needling the President for issues that Democrats know annoy him.

And it is apparent to anyone watching that Obama is enjoying the cathartic release.

“Can you imagine if I had a secret Chinese bank account when I was running for reelection?” Obama jokingly asked, citing a New York Times report about a previously undisclosed bank account Trump holds in China. “They would’ve called me Beijing Barry.”

That strategy will continue this weekend, when Obama joins Biden on the campaign trail in the key state of Michigan on Saturday.

An interview between basketball player LeBron James and Obama is slated to air on Friday, the latest example of the former president looking to engage young and Black voters for Biden.

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Obama’s decision to hold his rhetorical fire on Trump until late in the campaign, said a source close to the former president, was “by design.”

“He has been selective on when he has weighed in to preserve his ability to, in the home stretch, make the most pointed case possible about the current occupant of the White House and have people pay close attention,” said the adviser, who acknowledged that Obama is enjoying his role attacking Trump.

Obama’s goal, the adviser said, was to “leave a little in the tank” during the first years of Trump’s presidency so that he could “go there” once the election was on.

David Axelrod, a longtime friend and adviser to Obama, said Biden also needed to firmly establish himself as the party’s nominee before Obama stepped up his visibility. Axelrod dismissed any criticism that the former president hadn’t been active enough in this campaign, saying it would have been far riskier to emerge earlier, giving Trump more time to try to use Obama against Biden.

“In terms of his value, it’s been smart not to overuse him,” said Axelrod, a CNN contributor. “They’ve been using him in targeted digital appeals to constituencies that Democrats need to arouse in this election: young people and people of color, who did not come out in the numbers that Hillary Clinton had hoped four years ago.”

Former US President Barack Obama addresses Biden-Harris supporters during a drive-in rally in Philadelphia, Pennsylvania on October 21, 2020.

It is not as if Obama has stayed entirely silent throughout Trump’s presidency – the former president warned about the impacts of Republican efforts to repeal Obamacare in 2017, ratcheted up his attacks on Republicans during the 2018 midterm elections and delivered a sober but biting speech at the Democratic National Convention earlier this year. He has also participated in dozens of Democratic efforts to turn out voters in 2020, including digital ads for candidates across the country.

But all of those forays into politics pale in comparison with the unbridled nature of Obama’s critiques in the final days of the presidential campaign.

In Philadelphia last week, he questioned Trump’s tax policy and handling of the coronavirus, while delivering personal barbs like jabbing at shrinking ratings for the President’s speeches and town halls.

“Really?” Obama asked incredulously when he recalled that Trump had said there wasn’t much he would change about his response to the pandemic. “Not much? Nothing you can think of that could have helped some people keep their loved ones alive?”

Days later, Obama said Trump’s attempts to look tough are all a façade.

“He likes to act tough and talk tough. He thinks scowling and being mean is tough,” Obama said at a drive-in rally in South Florida before noting that Trump had abruptly ended a high-profile interview. “But when ’60 Minutes’ and Lesley Stahl are too tough for you, you ain’t all that tough.”

And in the latest example of Obama paying close attention to the day-to-day news around Trump, he mocked the President for lamenting that news outlets cover the coronavirus too much.

“More than 225,000 people in this country are dead. More than 100,000 small businesses have closed. Half a million jobs are gone in Florida alone. Think about that,” Obama said. “And what’s his closing argument? That people are too focused on Covid. He said this at one of his rallies. Covid, Covid, Covid, he’s complaining. He’s jealous of Covid’s media coverage.”

Former President Barack Obama walks on stage as he campaigns for Democratic presidential candidate former Vice President Joe Biden at Florida International University, Saturday, Oct. 24, 2020, in North Miami, Fla.

Obama spent years trying to hew to a long-standing tradition that former presidents avoid attacking their successors, routinely telling people that he appreciated the way George W. Bush mostly stayed out of electoral politics during his presidency. Trump, however, changed that calculation.

As one adviser put it: Trump has been a “norm-shattering President,” including the norm of former presidents avoiding directly attacking their successors.

Obama’s reemergence has delighted Democrats and clearly angered Trump, who has taken to tweeting about the former president as outlets like Fox News and others take his speeches live.

“Obama is drawing VERY small (tiny) numbers of people,” Trump tweeted around Obama’s speech on Tuesday. “Biden is drawing almost no one. We are drawing tens of thousands of people. You’ll see that again today. The Great Red Wave is coming!!!”

There has long been an imbalance in Obama and Trump’s relationship: The current President mentioned his predecessor far more than Obama mentioned his successor.

But this latest effort by Obama has shifted the relationship. Obama, after years of ignoring Trump incessantly pushing conspiracy theories about him, has used his onetime silence to elevate what he decides to say when it matters most.

As much as Obama is enjoying bashing Trump, this election will be a central test of the former president, who has to date been largely unable to transfer his popularity to other Democrats. This was clearest in 2016, when his frequent forays into the presidential campaign did not help Hillary Clinton get over the finish line, leading to Trump’s unexpected victory.