Why is Trump obsessed with leaving his mark on Washington?

After a crushing defeat in the US midterm elections that has weakened his political standing, President Donald Trump is doubling down on efforts to leave his mark on Washington. He has declared plans to designate the Oval Office as a national monument to preserve it in its current form, while accelerating a series of construction projects — including a grand banquet hall and a triumphal arch.

According to the Associated Press and other outlets, Trump signed a proclamation Thursday (local time) directing that the Oval Office and the Cabinet Room be preserved exactly as they currently appear.

Speaking to reporters in the Oval Office, Trump said he was "making this a national monument" and vowed that "nobody will be able to touch it."

Trump toured the construction site of a large banquet hall being built in the East Wing of the White House on Thursday. It was his only public appearance the day after his midterm defeat was confirmed — an unscheduled visit.

On Monday, the day before the election, Trump held a news conference at the "reflecting pool" in front of the White House as the final stop of his campaign. The choice of venue drew puzzled reactions from the press. Trump used the occasion to tout his renovation of the large pool situated between the Lincoln Memorial and the Washington Monument, two of the capital's most prominent landmarks.

A real estate developer by background, Trump has long shown a particular fondness for grand and ornate architecture. He recently showed off a marble-finished helicopter landing pad on the White House lawn to Chinese President Xi Jinping, who visited the United States last month.

An avid golfer, Trump also moved to convert a public golf course in central Washington — East Potomac — into an upscale facility, ordering unauthorized tree removal. A court has since blocked the effort.

Trump's attempts to attach his name to landmarks around the capital have also continued. A prominent example was his push to add his name alongside that of the Kennedy Center, Washington's performing arts venue. That, too, was blocked by a court.

Why is Trump so fixated on physical legacy? Analysts offer two competing explanations: a desire to be remembered as a great president after leaving office, or simply the instincts of a lifelong real estate developer.

CNN has cited a source as saying that the East Wing banquet hall "will not be able to be torn down" by any successor, calling it "a permanent imprint" Trump is leaving behind. "What he cares about is the question of legacy," the source said.

Another legacy project — a large triumphal arch in Washington — may be moving toward construction soon. The National Capital Planning Commission, whose chairman is a Trump ally, held a meeting Friday and appeared set to approve the project, according to the AP.

The roughly 76-meter arch is one of Trump's signature initiatives. It faces opposition and legal challenges over concerns that it would worsen traffic, clash with the surrounding landscape and pose safety risks to aircraft approaching and departing a nearby airport.