American politics officially has gone full circle in 12 years that often have felt like double that.

The United States a decade ago had a black president, Barack Obama, in the White House who was accused by Republicans of lying to them about being able to keep their doctor under a health care reform plan known as "Obamacare" that he later signed into law.

The United States today again has a white president, Donald Trump, in the White House who Democrats say caters to white nationalists and on Thursday night suggested Americans put "disinfectant" into their bodies via "injection" to kill the coronavirus, a trial balloon immediately rejected by doctors -- even the ones trying advise him on the Covid-19 crisis.

"If you like the plan you have, you can keep it. If you like the doctor you have, you can keep your doctor, too," then-President Obama said in June 2009, as he and House Democrats worked on the Affordable Care Act.

Nearly 11 years later, it was not the cerebral and methodical 44th president guiding the country through another crisis, but the impulsive and aggrieved 45th.

One critique of Mr Obama's presidency was his tendency to listen too much, and to think too much. He chewed over big decisions, and often appeared reluctant to make the final call.

Mr Trump is the polar opposite.

Where Mr Obama would bring in experts from inside the government, academia and the private sector before making a policy decision or public announcement, Mr Trump goes with his gut.

Thursday night's White House coronavirus press conference was the final stretch of concrete -- Mr Trump likes to remind everyone he's "a builder," after all -- in America's circular political highway.

The president poured the final section himself. It did not appear planned. Rather, the circle completed -- to borrow a phrase from Dave Eggers' 2013 dystopian novel The Circle -- when Mr Trump heard a single word. Ironically, it came from the mouth of an official -- no, yet another "acting" one -- from the Department of Homeland Security, of all agencies, who was summoned to the James S Brady Briefing Room to discuss a "study" commissioned, it appeared, to justify the president's previous claims that, as Vice President Mike Pence diplomatically put it Thursday evening, "heat and sunlight" could end the pandemic outbreak in the U-S-A.

"We are also testing disinfectants, readily available. We have tested bleach, we have tested isopropyl alcohol on the virus specifically in saliva or respiratory fluids. I can tell you that bleach will kill the virus in five minutes, isopropyl alcohol will kill the virus in 30 seconds -- and that is with no manipulation no rubbing, just spring it on and leaving it go," William Bryan, the acting DHS official, said.

If it was not clear to anyone listening, including the president who was standing mere feet away, that Mr Bryan was describing applying such cleaning formulas to a surface that had become contaminated with Covid-19 after a human had ejected it onto said surface, his next utterance should have.

"You rub it and it goes away even faster," he said. "We are also looking at other disinfectants, specifically looking at the Covid-19 virus in saliva."

It turns out Mr Trump, who has zero medical training, is, too.

"And then I see the disinfectant, where it knocks it out in a minute, one minute. And is there a way we can do something like that by injection inside or almost a cleaning, because, you see, it gets in the lungs and it does a tremendous number," Mr Trump said.

He then instructed his top public health officials -- including coronavirus task force member Deborah Birx, a physician who sat statuesque nearby as the president suggested Lysol or 409 injections as Covid-19 treatments -- to "check that."

Mr Trump then again tried to portray himself as something of a medical and scientific savant -- he has done the same with the four-star officers he once referred to as "my generals," since replacing those who questioned his impulsive foreign and national security policy ideas with loyalists.

"So, you are going to have to use medical doctors with, but it sounds interesting to me," he said matter-of-factly. "So we will see."

What we see is yet another attempt by the White House to minimise the damage from one of the most eyebrow-raising moments of the Trump term.

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"President Trump has repeatedly said that Americans should consult with medical doctors regarding coronavirus treatment, a point that he emphasised again during yesterday's briefing," new White House Press Secretary Kayleigh McEnany said in a Friday morning statement. "Leave it to the media to irresponsibly take President Trump out of context and run with negative headlines."

The president did say, later in the briefing as astonished reporters sought clarification, "it wouldn't be through injections."

"You're talking about almost a cleaning, sterilization of an area?" he asked Mr Bryan, who replied, "Right."

But the reality show president who is polling in the 20 per cent range when voters are asked if they trust what he says about Covid-19 already had injected more confusion and shock into the coronavirus crisis.

A brand new episode of the nightly Trump coronavirus variety show is mere hours away. From a president who wanted to get all Americans access to doctors to one who shuns their advice and speaks of disinfectant injections.