The Democratic measure was an amendment offered by Senator Jim Webb of Virginia, a former military man (and former Republican). His proposal sought to ensure a decent interval of "dwell time" at home for US soldiers before being sent back to Iraq. Democrats thought they had hit on an unassailable formula for being pro-troops while at the same time keeping pressure on the Bush administration. Republicans smelled a plan to render a sustained large troop presence unworkable.

Now, the US Senate is an oddly conceived body. It was chiefly a constitutional sop to small states with its assurance that each state would have two senators. But it was also designed to allow minorities to halt stampeding majorities. One senator can stop anything. As a result, through most of its history the Senate has been a deeply intransigent body, the reactionaries' last line of defence.

And since the Democrats took over this year, Republicans - under their leader, Mitch McConnell of Kentucky - have stalled so much that they're on pace to set a new record for blocked legislation by a factor of three. Then, having gummed up the works, McConnell et al turn around and accuse the Democrats of running a do-nothing Congress!

This, in a nutshell, is why the Democrats have not been able to end the war. Republican legislators know that, however unpopular the war may be, a united pro-war front might help the party keep the White House in 2008, because they can run on the accusation that the Democrats wish defeat and disgrace upon these great United States of America.

Here, Mrs Clinton enters the picture. Her near flawless campaign last week executed the near flawless unveiling of her healthcare plan. This was much anticipated, partly because of the dramatic failure in 1993-94 under her watch and partly because people wanted to see how ambitious she would be.

Lo and behold, the plan was much more far-reaching than anyone expected (and thus pleasing to liberals), and it avoided some of the errors of the past (thus passing muster with the pundit class). If Clinton actually becomes president, she will have laid a strong foundation from which to spring into action on the great piece of unfinished business of 20th-century American liberalism.

But ... those Republicans, and that Senate. It has gone down in history that Hillary blew healthcare the first time around because of her tone-deafness and unwillingness to compromise. But there's more to the story - much more.

Paul Starr was one of the Clinton administration's leading healthcare reform experts. Writing in The American Prospect, he argues convincingly that conservatives and Republicans were set against allowing the Clintons to pass any healthcare reform "because if it succeeded, it might renew New Deal beliefs in the efficacy of government, whereas a defeat of the health plan could set liberalism back for years".

That is the main reason the Clinton plan failed, just as current GOP obstinacy is the main reason the Democrats can't end the war. And if anything, Republican fear of liberal success is greater today, and will be greater in 2009, than in 1993, and they will fight any Democratic president tooth and nail. And the 47 million without healthcare, and the thousands dying in Iraq? As usual, they are beside the point.

michael.tomasky@theguardian.com