The prime lesson of the last 100 years for political leaders and heads of government is: if you go left you will take your country to economic failure.

It is a lesson that President Obama either has not learnt, or has learnt well and wants just that result.

At his second inauguration (painful words!), “the apostle of the ever-expanding state” delivered “an ode to collectivity”. So Charles Krauthammer writes.

The media herd is stunned to discover that Barack Obama is a man of the left. After 699 teleprompted presidential speeches, the commentariat was apparently still oblivious. Until Monday’s inaugural address, that is.

Where has everyone been these four years? The only surprise is that Obama chose his second inaugural, generally an occasion for “malice toward none” ecumenism, to unveil so uncompromising a left-liberal manifesto.

But the substance was no surprise.

After all, Obama had unveiled his transformational agenda in his very first address to Congress, four years ago. It was, I wrote at the time, “the boldest social democratic manifesto ever issued by a U.S. president.”

Nor was it mere talk. Obama went on to essentially nationalize health care, 18% of the U.S. economy — after passing an $833 billion stimulus that precipitated an unprecedented expansion of government spending.

Washington now spends 24% of GDP, fully one-fifth higher than the postwar norm of 20%.

Obama’s ambitions were derailed by the 2010 midterm shellacking that cost him the House. But now that he’s won again, the revolution is back, as announced in Monday’s inaugural address.

It was a paean to big government. At its heart was Obama’s pledge to (1) defend unyieldingly the 20th century welfare state and (2) expand it unrelentingly for the 21st.

The first part of that agenda — clinging zealously to the increasingly obsolete structures of Social Security, Medicare and Medicaid — is the very definition of reactionary liberalism.

Social Security was created when life expectancy was 62. Medicare was created when modern medical technology was in its infancy. Today’s radically different demographics and technology have rendered these programs, as structured, unsustainable. Everyone knows that without reform they’ll swallow up the rest of the budget.

As for the second part — enlargement — Obama had already begun that in his first term with ObamaCare.

Monday’s address reinstated yet another grand Obama project — healing the planet. It promised a state-created green energy sector, massively subsidized (even as the state’s regulatory apparatus squeezes fossil fuels, killing coal today, shale gas tomorrow).

The playbook is well known. As Czech President (and economist) Vaclav Klaus once explained, environmentalism is the successor to failed socialism as justification for all-pervasive rule by a politburo of experts. Only now, it acts in the name of not the proletariat but the planet.

Monday’s address also served to disabuse the fantasists of any Obama interest in fiscal reform or debt reduction. This speech was spectacularly devoid of any acknowledgment of the central threat to the postindustrial democracies (as already seen in Europe) — the crisis of an increasingly insolvent entitlement state.

On the contrary. Obama is the apostle of the ever-expanding state. His speech was an ode to the collectivity. …

For Obama, nothing lies between citizen and state. It is a desert, within which the isolated citizen finds protection only in the shadow of Leviathan.

Put another way, this speech is the perfect homily for the marriage of Julia — the Obama campaign’s atomized citizen, coddled from cradle to grave — and the state.

In the eye of history, Obama’s second inaugural is a direct response to Ronald Reagan’s first. On Jan. 20, 1981, Reagan had proclaimed: “Government is not the solution to our problem, government is the problem.”

And then he succeeded in bending the national consensus to his ideology — as confirmed 15 years later when the next Democratic president declared, “The era of big government is over.”

So said Bill Clinton, who then proceeded to abolish welfare. Obama is no Clinton. He doesn’t abolish entitlements; he keeps old ones and creates new ones to pursue a vision of a more just social order where fighting inequality and leveling social differences are government’s great task.

Obama said in 2008 that Reagan “changed the trajectory of America” in a way that Clinton did not.

He meant that Reagan had transformed the political zeitgeist, while Clinton accepted and validated the new Reaganite norm.

Not Obama. His mission is to redeem and resurrect the 50-year pre-Reagan liberal ascendancy.

And take it as far left as he possibly can. To mold a poorer, more subservient, more weakly defended, mediocre America under dictatorial government.

How far will Americans let him take them in that direction?