And why not? In the first round Mr Duda might have beaten the incumbent by less than one percentage point on a turnout of less than half of Poland's registered voters. In other words, less than one in six of all Poles voted for Mr Duda in the first round. Clearly, thought President Komorowski's advisors and supporters, in the second round, as long as enough of the remaining five-sixths who didn't vote Duda in round one turned up to vote rationally, the right result would be assured.
Bearing in mind that third place in the first round was taken by some pop singer, and the supporters of pop singers tend not to see eye-to-eye with religious conservatives, it was assumed [by whom? by the chattering classes] that this element of the disgruntled youth would see sense and support the status quo.
But it was not to be. As we now know, Mr Duda beat President Komorowski by two percentage points, the closest result in the history of post-1989 presidential elections.
On the part of Bronisław Komorowski and his team - complacency. The pollsters got it wrong. Far more wrong than the British pollsters telling the nation that Labour would beat the Tories on 7 May.
Not a single poll - not one - expected Mr Duda to win the first round. The last week's polling showed a comfortable eight to 12 points lead for Mr Komorowski from most pollsters, with only one outlier predicting a dead heat. [Yet on a ride in southern Mazowsze, between Białobrzegi and Warka, the weekend between the first and second round, I could only see posters for Duda. Not a single one for Komorowski.]
What could possibly go wrong? Back in February, pollsters were showing 65% support for the incumbent and a 40+ percentage point lead over the second-placed Mr Duda.
So what did go wrong? Too few PO activists and supporters considered the possibility than in a second round run-off (which was looking increasingly likely from late-March onwards, since when pollsters began suggesting that the president was unlikely to win in the first round), the young and disgruntled would cast their votes for a religious conservative candidate.
Why did they do so?
They took the bait, so sweetly laid. It was explained to them that the reason they were jobless or poorly-paid was because a callous, greedy elite was doing them down. The answer, suggested candidate Duda, is to redistribute. But not from rich to poor.
Reducing retirement age from 67 (for men and women) to 60 (for women) and 65 (for men). Despite the fact that Poles on average live six years longer than they did in 1989. Who's going to pay for this? Those Poles who are still working. And now they complain about low wages and high taxes.
In all honesty, the Polish state pension system will be unable to pay its obligations, and if the whole thing were to stick together, we'd need to be working to 72, not 67. So Mr Duda's promises are a case of kicking the can down the street, for our children's generation to pick up the tab. Big time.
No mention among Mr Duda's shiny promises of slimming down a bloated and inefficient public administration (which lazy, complacent PO have failed to do over the past seven and half year in offices).
No mention of spurring on Polish innovation by getting universities to focus on commercialising the brilliant ideas of their talented students (who have been tending to commercialise them abroad).
No mention of streamlining the red tape that holds back entrepreneurs from growing their businesses by taking on more employees.
So, to my shame, last Sunday Polish voters have followed those in Greece and Spain who've believed the Pied Piper politicians who promise them a painless road to a brighter tomorrow.
OK - let's step back. What does this really mean? What did last year's European Parliamentary elections mean to the UK? The largest party representing British voters, with one-third of all UK seats in Brussels, is UKIP. Which was slaughtered in the general election earlier this month. Why did Brits vote for UKIP in the Euro-elections? Because 'it's a protest vote'. And because 'the European Parliamentary elections don't matter'.
Do the Polish presidential elections matter? In terms of how the outcome affects the nation, nowhere near the same extent as the American or French presidential elections. More akin to the German or Italian ones.
Does this election mean that PiS can win an outright victory in the parliamentary election this autumn? PO has suddenly and violently been woken up from its lethargic complacency. For years it has been winning elections by saying 'if not us - that lot', pointing at Messrs Kaczyński, Macierewicz and Ziobro. This worked as long as Jarosław Kaczyński was the public face of PiS. But by fielding a man one generation younger, the spell was broken.
Mr Duda's victory is a like a window opening and letting in a sharp, icy gust of wind into a stuffy, airless room full of the same stale breath.
The big unknown unknown between now and the autumn is whether a new party, akin to the now largely defunct Ruch Palikota, will emerge to occupy the economic and socially liberal quarter. (We must learn to stop talking about 'left' and 'right' and look at politics in a two-axis way).
Mr Duda and PiS occupy the socially conservative but economically socialist quarter. The old communists, the SLD, socially liberal but economically socialist, were annihilated in this election. PSL, the 'peasants' party' is an old-school jobs-for-the-boys who'd join any coalition just to keep its placemen in jobs.
PO have held the centre ground, with a large measure of success compared to other countries in the EU, none of which can boast the same economic record from 2008 to today.
So - there's a vacancy in the top-right quadrant. Will Mr Pop-singer be in time to set up a party to occupy this ground? Or will former finance minister and reformation hero, Prof. Leszek Balcerowicz and economist Ryszard Petru ride to the rescue of fiscal prudence and financial rectitude?
The next six months will be extremely interesting - not to say fraught. Everything is at stake. The progress that Poland has made in rebuilding its economy can come spluttering to a halt if a redistributionist government pull all the wrong macroeconomic levers.
If there's one thing worse than outright liars at the helm, it's amateurs.
This time last year:
Call it what it is: Okęcie
This time two years ago:
Three stations in need of repair
This time three years ago
Late evening, Śródmieście
This time foure years ago:
Ranking a better life
This time sixe years ago:
Paysages de Varsovie
This time seven years ago:
Spring walk, twilight time