There are two chants that everyone remembers from Donald Trump’s campaign rallies. One is “Lock her up!”, aimed at Hillary Clinton, a demand not likely to be met unless America becomes a banana republic. The other is “build that wall!”

It is now crunch time for this central, defining promise of the Trump candidacy and “make America great again” movement. The US president says he will not support a bill to fully fund the government until he secures $5.6bn for a wall on the US-Mexico border.

So quarter of the US government has been shut down for two weeks, leaving hundreds of thousands of workers without pay. After Friday’s talks with congressional Democrats at the White House, there is still no end in sight.

Indeed, no one should assume Trump was bluffing when he said he was willing to keep the government closed for months or even years, or that he would consider using emergency powers – an ominous phrase in any democracy under strain - to bypass Congress and get the wall built.

It has come to this because there is no political incentive for Trump or his nemesis, the newly re-elected House speaker Nancy Pelosi, to blink first. Both are under intense pressure from their respective bases to hold firm and resist concessions. The system has delivered divided government with no common ground.

On Thursday, Vice-President Mike Pence told Fox News: “Bottom line, if there’s no wall, there’s no deal.” Pelosi, meanwhile, told reporters on Capitol Hill: “We’re not doing a wall. Does anybody have any doubt that we are not doing a wall?”

A foreign visitor to the US might not immediately spot the signs of malaise. In grey and chilly Washington, traffic still rolls, trains still run, the shows goes on. The current shutdown has not affected three quarters of the government, including the Pentagon and the postal service, which have secure funding.

But there is a gradual sense of things grinding to a standstill, small but telling harbingers of imperial decline. The Smithsonian Institution’s 17 museums and zoo are closed (although the animals are still getting fed). Couples in Washington cannot get marriage licences.

Nationally, 800,000 employees from the departments of homeland security and transportation and other agencies have been furloughed or are working without pay. Even as China lands a spacecraft on the far side of the moon, most employees at Nasa are on furlough, with the small percentage who remain working without pay.

With bitter irony given the issue at hand, the shutdown has reached America’s 62 immigration courts. Hundreds of judges are on furlough, and only cases of immigrants in detention are being heard.

The National Park Service is operating with a skeleton staff. Some parks may be accessible, others closed completely. The National Park Service is providing no visitor services such as toilets, facility and road maintenance and trash collection. Campgrounds have begun closing due to sanitation concerns.

As the shutdown drags on, there will be a creeping paralysis, affecting everything from the Internal Revenue Service’s ability to pay out tax refunds to rental assistance payments in public housing to whether the interior department can pay out treaty rights obligations to Indian tribes.

The fact it is a partial, not total, government shutdown has perhaps tempted Trump to make a political calculation that the pain is preferable to giving in – or being seen to give in – on his promise to build the wall. It is worth remembering how fundamental this was to his campaign, his political identity, perhaps even his psyche.

On the day he launched his unlikely run for president, descending an escalator at Trump Tower in New York, Trump declared: “I would build a great wall, and nobody builds walls better than me, believe me, and I’ll build them very inexpensively, I will build a great, great wall on our southern border. And I will have Mexico pay for that wall.”

Mexico rejected the idea but Trump repeated the promise in almost every speech and interview, insisting the estimated $23bn barrier is necessary to stem the flow of illegal immigrants and drugs into the US. For supporters and detractors alike, it became the ultimate symbol of his xenophobic vision of America.

Democrats’ victory in the House in the midterms election means the dream has probably slipped away, but Trump cannot afford to admit it. When, last month, the Republican-controlled Senate approved a stopgap measure to keep the government open, he was poised to sign it until rightwing talking heads complained that he was capitulating.

In that sense, it is not a Trump shutdown or Pelosi shutdown. It is a Rush Limbaugh shutdown, an Ann Coulter shutdown. Rightwing minority rule is now holding the country to ransom.

For their part, Pelosi and the Senate minority leader, Chuck Schumer, see no reason to impose a medieval solution on a 21st century problem. They are also aware that Democrats were elected in 2018 by voters eager to resist Trump in general and the wall in particular. To give an inch would be seen as a betrayal. Pelosi declared this week: “How many more times can we say no? Nothing for the wall.”

On Friday, Trump and the Democratic leaders could not even agree whether their talks had gone well. Trump insisted the meeting had been “very productive”, whereas Pelosi described the conversation as “sometimes contentious”.

And where, in all this, is Mitch McConnell? The Senate majority leader has been lurking on the sidelines, saying little other than that measures approved by the House are non-starters in the Senate without the president’s support. The New York Times noted: “By absenting himself, Mr McConnell had hoped to push the blame for a prolonged shutdown on to Democrats while protecting Republicans running for re-election in 2020 – including himself.” But with some Republicans becoming restless, it is not clear whether the strategy is sustainable.

For now, Trump has designated a working group led by Pence, and including his son-in-law Jared Kushner, to conduct more negotiations. But the stalemate looks set to overtake the longest shutdown on record: 21 days under Bill Clinton in 1996.

The president’s best hope now is to turn the dispute to his advantage by using Democrats as a foil in the 2020 presidential election. The line of argument will be along the lines of: I wanted to give you a wall, but the Democrats denied me – and you. That is why, in the White House Rose Garden on Friday, he reiterated: “I’m very proud of doing what I’m doing.”