President Trump’s accusations of wiretapping reignited a long-simmering feud with former President Obama. Mr. Trump claimed Saturday that his predecessor engaged in McCarthyism and called Mr. Obama a “bad or sick guy.” The attacks broke an uneasy truce between the two men since the White House transition.

During the 2016 election, Mr. Obama was a harsh critic of Mr. Trump, and frequently campaigned against him. But their animosity goes back much further, when Mr. Trump led a fringe movement that refused to accept Mr. Obama’s American citizenship, reports CBS News correspondent Chip Reid.

After the November vote, the then-president-elect praised the man he once called the “worst president” in U.S. history. Mr. Trump and Mr. Obama spoke regularly prior to the inauguration and appeared to have buried the hatchet.

“He is engaging and gregarious,” Mr. Obama told ABC News in January.

“You like him?” George Stephanopoulos asked.

“You know, I’ve enjoyed the conversations that we’ve had,” Mr. Obama said.

On the “O’Reilly Factor” in February, Mr. Trump told the host: “We get along. I don’t know if he’ll admit this -- but he likes me.”

But with his presidency now bogged down by protests and allegations of Russian collusion, Mr. Trump has taken the gloves off.

“I think that President Obama is behind it, because his people are certainly behind it, and some of the leaks, possibly, come from that group,” Mr. Trump told Fox News.

Mr. Trump now accuses Mr. Obama of directing a Watergate-like conspiracy, something the former president denies.

USA Today Washington bureau chief Susan Page said Mr. Trump has defied a presidential tradition of not personally attacking your predecessor.

“Even President Obama, when he took over, was critical of President George W. Bush,” Page said, “but he never criticized him personally in the way President Trump has now criticized President Obama.”

The two most recent presidents have been at odds since Mr. Trump was the face of the birther movement.

“No one is prouder to put this birth certificate matter to rest than the Donald. And that’s because he can finally get back to focusing on the issues that matter -- like, did we fake the moon landing?” Mr. Obama joked at the White House Correspondents’ Dinner in 2011.

“Whether President Obama and President Trump will ever really become friends, that is too far in the future to even speculate about,” Page said. “Also maybe hard to imagine, but we’ll see.”

Outgoing presidents usually move out of Washington to clear the way for their successor. Mr. Obama has chosen to stay in the capital and launched a Democratic Party initiative on redistricting. He also recently praised opponents of Mr. Trump’s travel ban.