Barack Obama’s campaign is taking on that horrible feeling familiar to those who followed Michael Dukakis back in 1988. First his huge summer polling lead has succumbed to gravity. And like Dukakis, Obama has now ‘fessed up to the repeated criticism of both Democrats and Republicans that he isn’t experienced enough, and picked an old senator to balance his ticket.

At least the little Greek from Boston got his vice nomination right. Worldly-wise, affable, moderate but politically hardened, Lloyd Bentsen was superior to everyone else in the 1988 race. His best moment wasn’t his Kennedy put-down of Dan Quayle, but when he took a question about an unsavoury campaign finance event in the same debate, disarming the issue by declaring, “I don’t make many mistakes but that one was a real doozy.”

Joe Biden is, alas, no Lloyd Bentsen. He’s about as exciting as the botched announcement of his nomination, which had all the suspense of those unmaskings at the end of Scooby Doo that invariably revealed the villain was Old Man Withers the amusement park owner.

Even if we overlook Biden’s repeated plagiarism offences that rightly ended his own presidential hopes (in 1988, curiously), all he does is draw attention to how insubstantial Obama is on foreign policy. Biden doesn’t even bring a major state with him — despite efforts to paint him as the “third senator for Pennsylvania”, Biden will only be bringing the great state of … Delaware to the contest. And it doesn’t do much for the theme of “change” if a vote for Obama is a vote for an old white Senate veteran as well.

Which is a problem, because excitement and change are Obama’s big themes.

The unpalatable reality for Democrats, a truth much explained away and much ignored, is that they should be looking at a landslide of LBJ proportions that hands them the White House and control of Congress for years.

The Republican brand is toxic, the US economy is on the slab and John McCain has to share the stage with a president about whom the only serious debate is whether he is the worst ever. That some polls have McCain ahead suggests that Hillary Clinton and her supporters were right — Obama can’t win what should be an unloseable election.

I thought Obama’s unelectability would proceed from the onslaught the Republicans, even in their weakened state, would unleash on him. But so far — that “celebrity” attack ad apart — it’s Obama’s own weaknesses that have plagued him, particularly when his lack of substance on foreign policy was inconveniently exposed by the Russian attack on Georgia.

It was always the case that McCain would revel in such an opportunity to ramp up his foreign policy credentials, but Obama played into his hands, simpering at first that it was “important for all sides to show restraint”. That sort of six-of-one-half-a-dozen-of-the-other-let’s-workshop-that-idea moderation was quickly left behind by Obama but the damage was done. He was tested and failed miserably.

Hillary Clinton, conscious of McCain’s foreign policy advantage and anxious to make up for her “under fire in Bosnia” disaster, would’ve been demanding to know why Dubya wasn’t challenging Vladimir Putin to join him in the boxing centre in Beijing to sort it out mano e mano, and offering to take Vlad the Impaler on herself if he wouldn’t.

Naturally, Obama’s supporters would argue that that is exactly the kind of playground mentality that their candidate will rise above, taking the world to a new era in which soaring rhetoric will heal all divisions. Which also explains why Obama’s supporters are perceived as elitist wankers.

And you can bet Clinton, who is not the nominee only because John Edwards lied about his infidelity long enough to cruel her run, wouldn’t have been ill-advised enough to undertake a presidential visit to Europe seven months before her inauguration like Obama did back in July.

Clinton was the real balance that the Obama ticket needed. Biden won’t bring over those Clinton supporters furious at the perceived dudding of their candidate before she could become the first female president. Nor will he convince swinging voters, wondering if the young guy fills the chair enough and who’ve endured eight years of rule-by-veep from Dick Cheney, to vote Democrat. But Biden, unlike the Clintons, doesn’t pose a threat to Obama, and therein lies the entire explanation for his selection.

McCain has his own problems with his base, especially the life-begins-at-ejaculation wingnuts of the Religious Right, but they hate Obama more than Democrats hate McCain. Obama has botched his veep opportunity. Let’s see whether McCain manages his balancing act better.