At 50, observed George Orwell, "everyone has the face he deserves". Unusually for that godliest of lefty seers, he was wrong. Rupert Murdoch passed that milestone three decades ago with no appendages emerging from his temples (although in Orwell's defence, he may have endured a pioneering double hornectomy).

With Barack Obama, on the other hand, Orwell was broadly correct. The President hits the half-century tomorrow with the handsome, placid features he deserves. It is the fizzog of a gentle, decent if intellectually arrogant man, untormented by the self-loathing that made Nixon look so cruelly vulpine, and free from the lupine seediness that hinted at Bill Clinton's appetites long before that woman Miss Lewinsky's blue dress went to the DNA analysis section at Sketchley's.

Signs of middle age are evident, it's true, from the rapidly greying hair and heavy creasing at the sides of the mouth. But his face remains enviably unravaged by the sleep deprivation and unimaginable stresses imposed by the rapid imperial decline set in motion by his predecessor's monstrous cabal.

Michelle certainly likes it. "She still thinks I'm cute," said Obama the other day. "And I guess that's all that matters, isn't it?" Well, no, you felt, it isn't. Other things matter too: things such as his fiscal capitulation to the terrorist far right that will rob tens of millions – the very people on whose primary behalf he ran for president – to ensure that the rich, mega-rich and hyper-rich continue to pay a smaller proportion in tax than the average American nurse. Looking at that face today, in fact, the only way it could conform more precisely to Orwell's dictum is if, in the next 12 hours, his liver succumbed to the jaundice that turned it bright yellow. For this was a heartbreaking act of skin-saving cowardice.

I hate to come over all crudely simplistic about an event of byzantine complexity, because the cards Obama held were, like so many of the hands dealt him since taking office, close to unplayable. As Sarah Churchwell brilliantly wrote on these pages yesterday, there is no negotiating with as delusional, anti-democratic and rank ignorant an entity as the Tea Party. These people are the modern version of Samson, literature's first suicide bomber, and would bring the temple down on themselves to kill the enemy, be that the concept of taxation itself or a black leader, or both.

Obama survived by placating them. He may even, though it is far too soon to tell, have narrowed the odds on his re-election. If he has simultaneously repositioned himself as a centrist and highlighted Republican extremism, as Bill Clinton did to propel himself to a 1996 landslide after Newt Gingrich shut down the federal government, it may yet be seen as a masterstroke.

Yet sometimes intricate political calculation feels somewhere between despicably small-minded and blindingly irrelevant. Sometimes, there is nothing for it but to be clumpingly simplistic, and crudely state that those of us who fell in love with the promise of Obama the candidate can no longer blind ourselves to the reality of Obama the President. Governing in prose is one thing. Preferring weasel words to governing at all is another.

This column comes in sorrow rather than anger. He is, as I said, a good man, and who believed that one of those could win the White House? But no more than noble intent and high intellect is goodness enough. As the age of American hegemony implodes, war is being waged in the US between progressive and reactionary forces. In allowing the latter such an unmitigated triumph, he first retreated, then first went missing in action, and finally resurfaced to claim victory. All politicians do that, you might say, and therein lies the peculiarly tragic nature of this presidency. What was Obama, after all, if not the alternative to all politicians?

He could have drawn a line in the sand. He, who claimed he'd rather be a transformational one-term president than a two-term duffer, could have said, "You didn't elect me to preside over a brutal diminution of the rights of the needy, and I won't have it" and risked himself in the fight to spread the pain between poor and wealthy. He might have lost and become unelectable – even been forced to stand aside in 2012 for Hillary Clinton.

And would that be such a terrible thing? Hillary is not, one suspects, a good woman. There is little, if anything, she would not baulk at in pursuit of power. But whatever her moral elasticity, Hillary is a street-fighter, and would never have surrendered to the Tea Party's pulverising nastiness and juggernaut stupidity. If the Republicans take the Senate next November and have control of both houses, who would you back to defend Obamacare?

Perhaps even at this late stage, liberal outrage at this repugnant deal offers her an opening for a primary challenge. If she stood and won on the, "I told you he wasn't up to it last time, but would you listen?" platform, the irony that would accompany Obama's cute face out of the Oval Office would be as depressing as any in memory.

The man elected as the peacenik, ultra-liberal enemy of entrenched poverty would be remembered as the ruthless Bin Laden assassin who presided over the most vicious assault on the poor in modern US history. Whatever the future holds for the one-time reincarnation of JFK, tomorrow no one other than Michelle will be tempted to sing "Happy Birthday Mr President" in the breathily adoring tones of Marilyn Monroe.