ON TUESDAY, beginning before dawn in seaside villages along the coasts of Maine and Connecticut, and ending after sunset 18 hours later on the westernmost of the Aleutian islands in the North Pacific, 80 million Americans will go to the polls to determine the direction of their country for at least the next two years.

They will be picking tens of thousands of governors, state legislators, mayors, judges, county executives, prosecutors, coroners and others. In some states they will be voting to approve or reject proposals on issues such as abortion, stem-cell research, gay marriage and taxes.

But when the results pour in, all eyes will be on the Senate and House of Representatives in Washington. The indications are that disgruntled voters are ready to end the Republican Party’s hegemony of most of the past six years. The party’s leaders are readying themselves for the loss of at least the 15 seats that Democrats need to take control of the House. They are still optimistic that they will prevent the Democrats from taking the six Senate seats that would give them control of the Upper House, too.

For their part, quietly — they don’t want to alarm voters with excessive confidence — Democrats are talking about “the wave”. They are beginning to think that voter dissatisfaction is now so great that it could produce a political tsunami, approaching in scale the 1994 midterm elections, when Republicans took control of the House for the first time in more than 30 years and won a big majority in the Senate.

Such an outcome would have a profound effect on the policies that the divided American Government follows for the next few years in such globally significant areas as Iraq. It could alter the entire landscape of American politics in the run-up to the 2008 presidential election.

A faltering war and an unpopular President, proliferating scandals among Republican politicians, the bungled response last year to Hurricane Katrina and growing disillusionment among Republican supporters about their party’s direction have been reflected in the polls for months. But making firm predictions, even this close to the election, is still risky.

Unlike a national vote in Britain, US elections are a complex patchwork of often countervailing national and local politics, personalities and policies. Democrats may be riding a tide of anti-incumbent fever, but Republicans still hope that, for all their woes, they can convince enough people to turn up and vote.

No one seriously doubts that Republicans will lose ground in Congress. But how badly? The scale of the Democratic advance — and whether it produces majorities in one or both houses — will depend on four key areas.

Issues v Values There is little doubt that Iraq is uppermost in voters’ minds. In many states there are concerns, too, about the economy and disgust at financial and sexual scandals. If voters were to decide on the basis of these issues alone, the result would surely be a Democratic landslide.

But against that is the importance in US elections of voters’ “values”.

In some of the key Senate races, such as Tennessee and Missouri, where Democrats are hoping to win, conservative voters may be deeply unhappy with the conduct of the war and unhappy about what Washington has done. But many will still place the values that underpin their politics above the narrower issues of policy. Most of these voters are religious conservatives for whom matters such as abortion, stem-cell research and gay marriage count most — and they remain the Republicans’ most powerful electoral asset.

National v Local “All politics is local,” a famous Democrat politician once said. It was, of course, precisely half- true. Clearly, not all politics is local. National political issues, such as the war, have been central to most of the congressional campaigns around the country and many voters will be looking to send a signal to Washington about their dissatisfaction with America’s direction.

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