The Democratic caucuses and primaries in the United States are effectively winnowing out candidates to stand against President Bush in November's presidential election. Suddenly it looks as if he could be defeated - and clearly this has been the principal factor driving the choices made by Democratic activists.
Their determination and realism have put Mr Bush on the defensive, as polls show the leading Democratic candidate at this stage of the campaign, Senator John Kerry, could defeat him.
White House strategists have been surprised by his dramatic breakthrough. They had calculated it would be relatively easy to defeat Mr Howard Dean, the most radical candidate, simply by so labelling him. It will be much more difficult to make the same criticisms of Mr Kerry, should he consolidate his early lead this month and next. His attacks on the Iraq war are anchored authoritatively in his experience of the war in Vietnam - a fact that carries weight with voters increasingly concerned that Iraq was invaded and occupied on the basis of false intelligence and poor political judgment.
That Mr Bush felt it necessary to appear on an hour-long television show at the weekend justifying the war (and giving a different account of why exactly it was fought) displayed an unexpected defensiveness at this early stage of the campaign. But this remains his election to lose. Victory may not be determined by the Iraq war; but even if it is, current manoeuvres to have a troop withdrawal well under way by next September and military -political authority transferred to NATO and the United Nations by then will provide strong arguments to justify it. Domestic and economic issues loom large in the Democratic primaries, which are mobilising popular criticism and dissent that was to a large extent suffocated since the September 11th 2001 attacks on New York and Washington. There is a greater polarisation of opinion among the electorate on these issues - and on Mr Bush's personality and suitability for the presidency - than has been seen for many years.
Mr Kerry is expected to do well in the Virginia and Tennessee primaries today. A good performance by Senator John Edwards from North Carolina will prepare him for a boost in southern contests to come. Former general Mr Wesley Clark and Mr Dean are facing crucial tests of their credibility today and in Wisconsin next week, ahead of the jumbo "Super Tuesday" primaries on March 2nd. The United States' electorate badly needs the democratic contest and political argument brought to it by this campaign, after Mr Bush's easy political ride in 2002 and 2003.