What began as a surprisingly cordial rapport between President-elect Trump and his Democratic predecessor has devolved into an occasionally bitter public feud over who should be calling the shots as President Obama prepares to cede his power to someone with a fundamentally different plan for the country.
Although he has just three weeks left in office, Obama has pursued an aggressive slate of foreign policy moves, environmental rules and executive orders in an attempt to tie up the loose ends of his policy agenda before Trump can begin to dismantle it.
Meanwhile, Trump has already begun to pursue his own agenda — a course that has repeatedly brought him into direct conflict with the sitting president.
"There's no question that Trump is a unique animal, but what Obama is doing is unprecedented," said Ford O'Connell, a Republican strategist.
"You'd have to go back to 2008 and sort of see the transfer of power between Bush and Obama," O'Connell said. "Obama was grabbing headlines left and right…and in a lot of ways, Bush kept quiet and went off into the sunset."
But Obama and his team have been far from quiet in the waning days of his administration. The lame-duck president spent the Christmas holidays boasting that he could have beaten Trump had he run in 2016 and dramatically altering the U.S. position toward Israel by allowing the passage of a damaging United Nations Security Council resolution against the Jewish state.
Trump responded Wednesday by decrying Obama's "inflammatory" comments and blasting the "total disdain and disrespect" the Obama administration had shown Israel. He also disputed the notion that Obama could have won given the challenges facing Obamacare and the economy.
O'Connell said the incoming and outgoing presidents seem locked in a struggle for control of the media narrative with their escalating political moves and rhetoric.
"I do think that part of it is a battle for attention, which is unprecedented," he said.
Since their friendly meeting at the White House on Nov. 10, Trump and Obama have clashed over a number of the administration's eleventh-hour decisions.
Where Obama praised the "progress" in communist Cuba after Fidel Castro's death in late November, Trump threatened to reverse Obama's diplomatic overtures to the Cubans unless they offered the U.S. a "better deal."
Where the White House touted its support of the decision to block the construction of the controversial Dakota Access Pipeline in early December, the Trump transition team said it wanted to see the pipeline built.
And where Obama presented the evidence of Russian political interference on behalf of Trump as incontrovertible during a mid-December press conference, Trump questioned whether Russia was even involved in the cyber attacks on Democratic groups and operatives.
The White House has repeatedly warned Trump against resisting too many of Obama's parting shots, noting that "there's one president at a time" whenever the president-elect has expressed outrage over an Obama administration effort.
But the tacit approval of a swipe at Israel was enough to open a rift between the president, president-elect, congressional Republicans and even some congressional Democrats.
Incoming Senate Minority Leader Chuck Schumer, the highest-ranking Democrat in the upper chamber, called Obama's last-minute move "extremely frustrating, disappointing and confounding." He joined nearly all members of Republican leadership in condemning Obama's latest, boldest lame-duck decision.
Despite the public deterioration of his relations with the president, Trump has maintained that Obama is still polite in their private conversations.
On Wednesday, the president-elect said he and Obama had a "very, very good talk."
"I'm getting along very well with him, other than a couple of statements that I responded to," Trump said. "We talked about it and smiled about it."