If, as that most hoary of clichés goes, a week is indeed a long time in politics, then 500 days is an eternity.
et as we inch towards the 500-day mark in advance of the 2020 US presidential election, it looks as if Donald Trump's official re-election campaign, to be launched in Florida later today, is taking place under a cloud of negative polling and falling approval ratings.
The polls that emerged over the weekend don't paint a happy picture for a man who has often displayed an almost Comical Ali-esque refusal to accept the evidence in front of him.
In the case of Comical Ali, the hapless Iraqi general famously tried to dismiss rumours of American tanks being sighted in Baghdad, angrily dismissing such reports even as a US Abrams tank trundled into the background of his interview.
Where Comical Ali couldn't see the tanks that were literally right in front of him, Trump's power is to see things that don't exist - the debate over the attendance at his inauguration immediately springs to mind - and his undeniably impressive powers of self-delusion will need to work at their maximum to extract any positives from Sunday's Fox News poll.
According to that survey, Trump is now trailing in the slipstream of no fewer than five of the Democratic front-runners.
That the likes of Elizabeth Warren and Kamala Harris are just ahead of him, but still within the margin for error, will be something he can easily dismiss.
But the other two results, featuring the men most likely to run against him next year, will be a serious cause of concern for the more professional operatives working on his re-election team. The Fox poll placed Joe Biden ahead of Trump by 49pc to 39pc amongst registered voters, while Bernie Sanders also enjoyed a comfortable margin over Trump, by 49pc to 40pc.
Sanders certainly has the loyalty of the hard-left wing of the Democratic Party and the shining light of that hard-left, first time Congressional representative Alexandria Ocasio-Cortez, has enthusiastically endorsed him.
But such support, while important to that part of the party's base, is equally likely to alienate the swing voters and even those traditional Democrats who think the party has become too PC. That leaves the door open for Biden, and that's where Trump should be getting twitchy.
Both the Fox poll and a subsequent CBS poll place Biden ahead in the key battleground states such as Michigan, Pennsylvania and Wisconsin - conservative states where Bernie Sanders' brand of "democratic socialism" is simply seen as a fancy term for communism.
Biden, on the other hand, seems to know how to get under Trump's skin and even before the last election was held, senior Democrats were bemoaning the fact that it was Hillary Clinton and not Joe Biden (who dropped out of contention following the death of his son) who was running.
As I said in these pages a few months ago, the Democrats' best hope of unseating Trump is to go with Biden - a man who won't frighten the horses, as they say in Wisconsin.
But the first problem Biden faces isn't even the ultimate end goal of beating Trump - it's winning his own party's nomination.
Known by his supporters as 'Uncle Joe', and dismissed by his opponents as 'Creepy Joe', Biden is a touchy-feely politician of the kind no longer in fashion.
Reacting to a spate of videos showing him displaying a now-unacceptable level of tactile behaviour, he admitted: "I shake hands, I hug people, I grab men and women by the shoulders. It's the way I've always been", before adding defiantly: "I'm not sorry for anything I have ever done."
His rivals in the Democrats have already been busy digging up the dirt on him, and their efforts will have been matched by the Republicans' dirty tricks campaign team.
But in the context of some of the incumbent's previous views and behaviour towards certain women, if Biden can clear that first hurdle of his own party, then he has more than a puncher's chance of making it to the White House.
In the meantime, Trump will bask in the adulation of a packed house in Orlando tonight, but this campaign will be a totally different beast to 2016.
There is an obvious hurdle in the fact that he is now the incumbent. He can no longer portray himself as the plucky political renegade taking on the might of the Clinton Machine.
It shouldn't be forgotten that his best electoral asset the last time was actually his rival, and her astonishing efforts to scupper her own campaign.
Only American politics could produce a billionaire property developer and TV presenter and present him as a gutsy outsider. That tactic worked the last time, but it's a magic bullet that's no longer available to him.
Now he is the man with the target on his back and that is a pressure he hasn't felt before.
There are also increasingly serious concerns about his judgment in the ever-escalating tensions with Iran.
For example, most of his base don't care so much about him accusing the 'New York Times' of "treason" - in fact, many of them probably agree with him.
One of his major advantages when dealing with Clinton was her apparent eagerness for foreign intervention - the continent of Europe is still suffering from her disastrous escapade in Libya, for instance - while he firmly portrayed himself as a non-interventionist.
That policy endeared him to many in a war-weary America, but they will quickly turn on him if the US becomes embroiled in a disastrous and unwinnable war with Iran.
His strong point is still the economy, and the simple fact that most working Americans have seen an increase in their disposable income. But economies are ultimately beyond the control of any individual president and, as we know only too well in this country, circumstances can change dramatically and suddenly.
What many of his critics seem to have either forgotten, or never realised in the first place, was that every new attack they launch only hardens his support.
In fact, you could reasonably argue that, at this stage, the biggest threat to Donald Trump's second term is Donald Trump himself.
Having lived life as the Teflon Don, apparently able to skate away from every scandal without suffering serious damage, he has benefited from the fact that the opposition, for all their bluster, have yet to land a major, career-ending blow.
If there is a smoking gun somewhere, the Democrats better hope they can produce it in the next 12 months.
After all, when it comes to Donald Trump, everything we think we know about politics is wrong.
The most realistic hope for the Democrats is to go with Biden. But don't bet against the Dems cutting off their nose to spite their face.
