When George W. Bush left the White House in early 2009, he boarded a helicopter and went home to Texas, where he mostly remained silent about President Obama's actions.

This presidential transition is shaping up a little differently.

Rather than returning home to Illinois, President Obama is moving just down the street from the White House to a mansion in the tony Kalorama neighborhood.

And rather than remaining quiet, Obama, 55, who will become one of the youngest ex-presidents in history, has promised to dive in with grassroots liberals seeking to oppose Donald Trump, a man he has been feuding with for years.

Obama last week told his political arm, Organizing for America, that he is "fired up and ready to go," in leading the resistance to Trump, whose victory over Hillary Clinton devastated liberals.

Obama had apparently been preparing for a much quieter retirement from the White House, but Clinton's loss has changed those plans, he said.

Not only is Obama grappling with a Democratic party that lacks a new leader, but a Trump presidency coupled with GOP control of Congress virtually guarantees an effort to undo his signature achievements, including Obamacare, immigration regulations and a slew of environmental rules.

"I promise you that next year Michelle and I are going to be right there with you, and the clouds are going to start parting and the sun is going to come back out, and we're going to be busy, involved in the amazing stuff that we've been doing all these years before," Obama told downtrodden supporters on the call.

Not only is Obama poised to become the most politically active ex-president in modern history, his vice president is also vowing to stay involved in the Democratic Party.

Biden rejected efforts to get him to take the helm of the embattled Democratic National Committee, but an aide said he "intends to remain deeply involved in helping shape the direction of the Democratic Party moving forward."

All told, Obama and Biden may become the first ex-White House team to directly mobilize a party against their successor. And they may have a lot to mobilize against, since Trump has pledged to reverse so much of Obama's work.

For starters, Trump has promised as one of his first acts as president to sign a bill repealing the Affordable Health Care law, which critics believe is collapsing. Democratic strategist Christopher Hahn said Obama may weigh in on that move without directly targeting Trump.

"I think the president will express regrets about the healthcare law being repealed, but I don't think he'll be openly critical of Trump about that," Hahn told the Washington Examiner.

Other Democratic strategists predict Obama will jump right into the fray based on his history of attacking Trump.

During Hillary Clinton's White House run, Obama delivered sharp criticisms of Trump at stops around the country, calling him unqualified and lacking the right temperament for the job. Obama even questioned whether Trump should be entrusted with the nuclear launch codes.

"Judging by how zealously President Obama campaigned for Hillary Clinton, I strongly doubt the then ex-president will be able to keep his counsel or maintain studied silence as Bill Clinton and George W. Bush have done before him," Doug Schoen, a former strategist for President Bill Clinton, told the Examiner.

If Obama publicly reacts to Trump, it would break from a tradition that has been carried out for decades by most ex-presidents.

Jimmy Carter was the last president to publicly engage with his successor, and sometimes traded barbs with President Ronald Reagan. In 1982, for instance, he accused Reagan of "not accepting his responsibilities," according to the New York Times, after Reagan blamed the poorly performing economy on the Carter administration.

Carter continued to chime in over the years. He called President George W. Bush "the worst in history" when it came to international relations.

Reagan, George H.W. Bush and Clinton restored the practice of remaining silent, though Clinton in 2000 criticized George W. Bush in private conversations released recently by Clinton's presidential library.

But unlike those who left the White House before him, Obama has an unusually long history of feuding with his successor, who once questioned whether Obama was born in the United States.

Obama began publicly criticizing Trump at the White House Correspondents Dinner in 2011, where he ridiculed Trump over his quest to get the president to release his birth certificate.

Obama's take-down of Trump, who was sitting in the audience, included a parody picture of what a Trump White House would look like. The image showed the historic home decked out like a casino, the White House lawn converted into a golf course, and bikini-clad women bathing in the fountain.

"Say what you will about Mr. Trump," Obama told the laughing crowd, "he certainly would bring some change to the White House."

Regardless of their history and Trump's agenda, it would be inappropriate for Obama to attack Trump, now or in the future, Schoen told the Examiner.

"He does himself and his legacy no good to interpose himself into the ongoing political debate once he leaves office," Schoen said. "Donald Trump has earned, deserves, and should be the sole and singular voice for the U.S. after election day."