Yesterday, Barack Obama gained some much-needed kudos from the left by putting up Sonia Sotomayer as a nominee for the Supreme Court seat vacated by David Souter — a George HW Bush appointee who had turned out to be a liberal, rather than the conservative the Bushites had been hoping for, and who became more liberal as the years went by.

Souter hated DC and wanted to get back to his New Hampshire cabin, and had clearly been hanging on only in the hope that the Democrats would take the White House. Conservatives could have hoped that Obama would appoint a centrist judge, leaning towards Souter’s “realist precedentist” approach — i.e. you don’t overturn previous Supreme Court rulings, unless they were clearly nuts, wrong or corrupt.

Sotomayer hits three targets — as a woman, a Hispanic and “disabled” (she’s type one diabetic) – but I don’t think that was uppermost on Obama’s mind. Sotomayer is on record, actually on film, as saying “appeals courts make policy” — i.e. that the interpretive scope the US system gives higher courts effectively allows them to make sweeping social changes by virtue of what they rule to be unconstitutional — the best example being Roe vs. Wade, which relied on an implicit right to bodily privacy in chucking out anti-abortion laws.

Sotomayer’s remarks may well make a Senate confirmation hearing difficult for her, even with the Democratic party’s nominal hold of 60 seats — especially as she then giggled and said “I know I’m being filmed and I know we’re not supposed to say it but it’s true.” On the other hand her previous confirmation — to the appeals court — was won with the support of ten or so Republican senators who are still there. Indeed the major problem may come from the increasingly ornery centre-right Democrat senators — such as Ben Nelson from Nebraska, emerging as their de facto leader — who are elected from substantially Republican states.

Obama still doesn’t have what he needs — the death or resignation of a conservative justice, that would allow him to decisively tip the court one way. The next cab off the rank is Ruth Bader Ginsburg, who has had pancreatic cancer, and who also appears to have been holding on waiting for a change of President. Obama’s plan appears to be replace current “liberals” with two justices more activist and further to the left, and then fill a conservative spot with a liberal-centrist, to preserve the illusion that a bench stack isn’t on.

That would move the court decisively left, while also making a 5-4 swing back to the right on some issues — not key constitutional ones — possible, throwing the right a bone, splitting its forces in a confirmation, and avoiding nightmarish Clarence Thomas-style confirmation hearing (who is, undoubtedly, the worst justice to sit on the post Civil War court).

The weird thing about judicial politics is, of course, that they don’t easily map onto left-right positions. The issues at law are so abstract and implicitly philosophical that strange crossovers occur. Had conservative appointments David Souter and Anthony Kennedy been the reliable Tories their nominators assumed them to be, America would be a very different place now. But Souter’s move to the left wasn’t really a political shift as such — it was simply that a whole series of constitutional questions arose on the Supreme Court which he had never previously been called to dispose upon.

The judicial minimalism that attracted conservatives to him had a corollary — he wasn’t going to easily overturn previously established rights, even if they were slated as being products of “judicial activism”. Kennedy, slightly more reliable for the right on some issues, became a judicial wild card, a justice euphemistically called “creative”, as likely to be found in a 6-3 minority with princes of the shades Scalia and Thomas, or in 2-7 minority with core liberal Stephen Breyer.

All of which is the separation of powers working as it was intended to — a facility which obstructs progress and positive social change as much as it guarantees it — and there’s no guarantee that Sotomayer won’t do the same from the right.

There’s less likelihood however. Pace Planet Janet and Greg “Sheets” Sheridan, the Obama reconstruction of American social life and power is well underway. Sotomayer is a middle of the road judge on some issues, but rights-heavy on issues including the right to sue employers, federal government agencies, against the fashion of property confiscation in criminal cases, and in favour of the right to consider whether certain forms of testing, promotion etc embeds an ethnic bias. Her position on the bench may thus, eventually, swing a whole series of affirmative action etc style cases.

Add that to key appointees in offices like Labour and Environment, and the looming Employee Free Choice Act (which would make it more difficult for employers to break up unionisation processes) and Obama’s volunteer civil service group Alliance for America — which, as the right charges, is in many ways a covert political grassroots organisation on the government dime — and quietly, beneath the conventional politics, Obama is putting in place the mechanisms of a generation Democratic dominance of all three branches of US government. And, as far as foreign policy goes, I will be surprised if by late 2010, a Karzai-moderate Taliban coalition is not ruling Afghanistan.

I could be wrong. But let’s face it; compared to Greg and Planet, who have been ever-reliably wrong for the last five years, I’m usually right.