I have spent most of the past two decades in Washington. Never, though, do I remember a congressional vote in which interest has been as intense, the outcome as uncertain, and where there is so much at stake – in this case the management of a sector accounting for a sixth of the US economy, not to mention the future of a presidency.

The closest equivalent was Bill Clinton's 1993 deficit reduction package. Like healthcare, it was opposed by every single Republican. This weekend the crucial vote will be in the House, but back then the drama unfolded in the senate.

Then, as now, Republicans were united in opposition, predicting economic disaster. But Barack Obama will be heartened by what happened next: the Clinton bill set the US on the path to balanced budgets, and paved the way for years of sustained and strong economic growth.

Then, as now, no one could predict the outcome. Success was ensured only by the vote of Senator Bob Kerrey, Clinton's old rival from the Democratic primaries, who after weeks of public handwringing, concluded: "I cannot cast a vote that brings down your presidency." That meant a 50-50 tie, broken by the decisive vote in his favour from VP Al Gore, as president of the senate.

But the tensions today make those of 1993 pale, and so does the sense of history. If healthcare reform passes, Obama will have a win that transforms his presidency. More important still, the US will take a giant step towards joining at last the ranks of wealthy advanced countries that provide health coverage to all their citizens.

No wonder the White House is praying that, when the moment of truth comes tonight, wavering Democrats will make the same choice as Bob Kerrey 17 years ago.