Haven't we seen this movie before? Barack Obama has just proved his chasm-wide appeal again by conquering another Republican-red state – Mississippi – yet the battle for the Democratic nomination is set to stretch out on to the far horizon. As the comedian Bill Maher says, in a reference to John McCain's age, "It's a bad sign when the Democratic campaign is set to last longer than the Republican nominee." But the looming ending to this story feels flatly familiar – like a slo-mo remake of Florida in the year 2000.

It is clear the Clintons are determined to get this nomination, any way, any how. If they have to do it by falsely claiming to have won states like Florida and Michigan – where Obama's name wasn't even on the ballot, because there was an agreement by all the candidates to punish the states for holding early primaries – then they will. If they have to do it by overturning the will of the Democratic electorate by appealing to the unelected super-delegates – a group of party functionaries who seem likely to hold the balance – then they will. If they have to do it by pandering to racist sentiments – dismissing Obama as akin to the black firebrand Jesse Jackson, or by leaking images of Obama in African tribal dress – then they will do it.

Some American liberals have been suddenly, violently disillusioned by the Clintons' tactics over the past few months. But in reality, for people who could see beyond political tribalism, the nature of the Clintons has been plain for a long time.

Download the new Independent Premium app Sharing the full story, not just the headlines

The idea that Clinton was "the first black President" was always implicitly racist: so screwing around, riffing well in speeches and liking fried chicken makes you black now? In fact, Bill Clinton was prepared to lash black people whenever it was politically convenient, with the quiescence of Hillary. Just after receiving the Democratic nomination for President, Governor Clinton returned to Arkansas to authorise the execution of a black man, Ricky Ray Rector, who was so profoundly mentally disabled that he told the guards to keep his last meal so he could have it tomorrow.

Attacking blacks when an election neared became a habit: in 1996, Clinton signed a package of welfare reform that effectively abolished benefits for poor women after a two-year time-limit. They are disproportionately black – and as a recession hits now, they will suffer severely.

Of course you have to make compromises to achieve power. But at some point, on some issues, you have to say – no, I can't. I can't execute this mentally disabled black guy. I can't plunge millions of kids into poverty. I can't still insist I was right to back the war in Iraq, when it has killed more than 650,000 Iraqis. The Clintons don't have that gagging reflex.

Instead, they chose to turn themselves into weathervanes, pointing whichever way the winds of mega-power blow them. This meant that on all the great issues of their time – global warming, spiralling inequality, the foolish "war on drugs" – the Clintons fed and fuelled the right. Hillary is following this approach to the letter. While promising in public to "take on the oil companies, the pharmaceutical companies", she is in fact shovelling more of their cash into her campaign than any other candidate, Democrat or Republican. Fortune magazine recently ran an adoring cover story calling her "the candidate of business".

Why did it take us so long to see them for what they are? Partly, it is because the Clintons were blessed with a parade of even greater grotesques as enemies. The right couldn't attack the Clintons on their genuine scandalous behaviour, because they supported it all: the executions, the abolition of benefits, the crackdowns. So they contrived nonsense scandals, like Whitewater and Monicagate. Today, many of them are serving up stale sexism against Hillary: right-wing host Tucker Carlson has announced, "There's something about her that feels castrating, overbearing and scary."

And partly, it is because the nightmare of the Bush years has made even the Clinton years seem like a halcyon heyday.

Think about the symbolism for the watching world if the Clintons manage to snatch this nomination. The people in a majority of states in America will have shown they are ready to embrace a black man as President – only for some white guys in suits to hand it to the wife of the ex-President. Their arguments in their own defence will seem feeble. The idea that Hillary is more "experienced" seems to me both anti-feminist and untrue. How does being married to a man make you "experienced" in his job? As the stand-up comedian Chris Rock said in a recent gig, "I don't get it. I've been married for 10 years – but if my wife came out here on stage now, you wouldn't laugh."

I am not starry-eyed about Barack Obama. He wouldn't have been my choice for nominee – I was a John Edwards man – and he has made plenty of ugly compromises himself. To give just one example: in 2005, he voted for the Class Action Fairness Act, which stripped away the ability of ordinary citizens to seek compensation from huge corporations. There was only one group who wanted this: the CEOs of the very Wall Street mega-firms that Obama takes millions from in practice today.

But there is considerable evidence that President Obama would be more susceptible to pressure from progressives than Hillary. To pluck one policy area: Bill Clinton increased jail terms for drug possession, creating a situation where one in nine black men between the age of 20 and 35 is now in prison at any given time. Obama, by contrast, was arguing for the full decriminalisation of marijuana as recently as 2004, and has refused to indulge in this deranged tough-on-crime escalation.

If the Clintons prevail, there will be a worse effect still: the US will be much more likely to have another Republican President. Most major polls show Obama is more likely to beat John McCain. The Republicans are desperate for a Hillary candidacy, knowing it is the one thing that can unite their base behind McCain. The far-right radio hosts Rush Limbaugh and Laura Ingraham have begged their listeners to go out and vote for her in the Democratic primaries; the National Review ran a front-page pleading, "Please vote for this woman".

Hillary would be unable to make an election issue out of McCain's greatest weakness – his support for the invasion of Iraq – because she (like me) made the same dumb mistake. She would have to fall back on reinforcing right-wing ideas by bragging about her "toughness". The enthusiasm Obama has stirred among first-time voters would leech away.

With their latest lunge at power, the Clintons have shown us how they should be remembered when the end credits roll – as a greasy stain on the bright blue dress of the Democratic Party.

j.hari@independent.co.uk