There are few who will deny the similarities between Donald Trump and former Italian Prime Minister Silvio Berlusconi.

Both grew their fortunes on allegedly mafia-linked real-estate developments, transitioned into successful careers as media moguls, and, against all odds, ascended to the helm of their respective national governments. Then there’s the common penchant for vitriol, misogyny, philandry, aggressive tanning, and pompous neckwear.

That's just the start. You could also include scapegoating immigrants, corruption, fake populism, attacks on the news media, etc.
There is also another similarity that is on the verge of repeating: The left's failed response to a corrupt demagogue.

Back in November, an Italian gave this advice.

Political opposition: ‘Stop crying and try to understand his voters’

For years, Berlusconi’s boorish behaviour was a gift to political opponents and journalists who were free to ridicule him. But ultimately they did not prove an effective opposition.

Opposing Berlusconi by ridiculing him, Orsina said, was a way to preach to the converted, as were attempts to warn that Berlusconi’s rule represented the end of Italian democracy.
“The most powerful way to oppose him, but it was never really done seriously, was to try and understand what his voters want and try to address the need of his voters. No jokes, stop shouting, stop crying, stop saying: ‘It is a horror and disaster’; try and seriously understand what his voters want, and the left was never really successful in doing that,” Orsina said.

Democrats were already preaching to the choir inside their bubble before the election. It didn't start with Hillary's 'deplorables' comment.
It seems to be getting worse.

“The question neither Maloney nor Luján will answer is whether they should recruit moderate to conservative candidates in rural districts or just abandon them altogether,” reported The Washington Post in an article titled, “Should House Democrats write off rural congressional districts?” This piece, and the DCCC strategies it outlines, embodies what is wrong with the Democratic Party: Their elitist arrogance is why Hillary Clinton lost the presidential election and why the Democratic Party is in the position it is in now.

This elitism and arrogance is on display almost every night on cable TV.
Trevor Noah’s Daily Show, Samantha Bee’s Full Frontal, and John Oliver’s Last Week Tonight are full-throated liberal polemics against Trump. Fair 'nuff. Trump is an easy target and much deserving of the abuse, even if it does devolve into childish name-calling at times.
That isn't the problem.

But somewhere along the way, the hosts of the late-night shows decided that they had carte blanche to insult not just the people within this administration, but also the ordinary citizens who support Trump, and even those who merely identify as conservatives....
Though aimed at blue-state sophisticates, late-night comedy shows are an unintended but powerful form of propaganda for conservatives.

This is the end result of a belief system built upon moral superiority. It only works if it is unquestionably morally superior (which it isn't), and even then the lack of humility is a huge turn-off.
Liberals can't see it because they are too busy signaling their virtue to each other.

Jacobin Magazine has a great article describing how the left in Italy has already gone down this road and completely failed. Can we learn from their mistakes?

Faced with a non-politician turning public life into the stage for his crass performances, the center-left, however, proved unable to propose a political alternative that went beyond decrying Berlusconi and his malign associates.
Moreover, given the Democrats of the Left’s open embrace of the Blairite-Clintonian Third Way, with the party’s former Communist leaders now abandoning the legacy of Antonio Gramsci in favor of managerial neoliberalism, they had no basis to oppose him with an alternative economic agenda...
As the powerful but brief surges of anticapitalist and antiwar mobilization dissipated over the 2000s, Italian liberalism increasingly settled into its own moralistic-judicial battle against Berlusconi, devoid of any wider social content. This was true not only of the Democrats but also of separate so-called “citizens” movements’ against Berlusconi such as the girotondi (“human chains”) protests starting in 2002, or, from 2009 Il Popolo Viola.

Sound familiar?

To persist in the “offended liberal defends institutional values” approach to politics is to disregard everything we see all around us, from Brexit to Duterte to Le Pen to Trump. It is to imagine that the attempt arbitrarily to define the boundaries of “legitimate” political discourse can dam a wave of populist reaction.
In this regard the Italian case presents a dire warning, even despite Berlusconi’s ultimate ejection from office. Today as the Democratic Party-led coalition continues its program of tearing up postwar labor rights, detaching his party from any vestigial attachment to the Left, the mass opposition to him comes not from social movements or Rifondazione Comunista, but an individualist and often ugly populist reaction, winning huge support even in the historic “red” bastions of Northern Italy.

Where the Democrats have moved to occupy the centrist and center-right political space now left by Berlusconi’s ailing party, the leftists who joined their anti-Berlusconi crusade now lie in ruins...
The Left’s alignment with neoliberal centrists against Berlusconi did nothing to thwart right-wing populism or keep racism out of politics. It guaranteed these forces’ unchallenged hold over millions of voters, while destroying its own alternative voice. Looking over the wreckage of the 2016 campaign, the US left must avoid making a similar mistake.

The neoliberal wing of the Democratic Party must be defeated, and it must be defeated soon.