President Bush will criss-cross the American Midwest today, rallying support as candidates in next week's mid-term elections enter the last stretch of the most expensive congressional elections in history.

Mr Bush's whistle-stop tour, which will pass today through the battleground states of Missouri and Iowa, coincides with last explosion of campaign spending, which is expected to see more than 600 advertisements launched on television and carry the cost of the elections beyond the $2.2 billion spent four years ago.

Mr Bush began the final, 10-state tour yesterday, leaving the White House and flying to Montana where he lent his support to the troubled campaign of Conrad Burns, a Republican Senator struggling to keep power in a reliably Republican state after he was linked to the scandal around Jack Abramoff, a corrupt lobbyist.

Mr Burns holds one of as many as nine Senate seats that could swing either way in next Tuesday's election and are being subjected to a barrage of rallies, radio and television advertising and endless, breathless polling as Democrat and Republican strategists plot the last hours of the campaign.

Riding on disaffection at the Iraq war and the perceived corruption of a Republican-controlled Congress, polls have for weeks predicted that the Democratic Party will retake control of the House of Representatives and challenge for a majority in the Senate, where it needs to gain six seats.

Last night, Mr Bush flew in the heart of the contest, telling a partisan, cheering rally in Billings, Montana: "I know you’ll join me in sprinting to the finish line."

"We will win the Senate and we’ll win the House. And we’re going to win these elections because we understand the values and priorities of the American people."

Since retaking control of Congress in a landslide set of midterm elections in 1994, the Republican Party has consistently outperformed the Democrats in elections, raising more money, campaigning more ruthlessly and compelling its members and supporters more effectively to the polls on election day.

Now, facing what pollsters have called the possibility of a "once-in-a-generation" defeat at the hands of the Democrats, Washington analysts have described the last stretch of the campaign as a battle between a swell of popular sentiment against the Bush Administration and the well-organised Republican party machine.

Yesterday, the First Lady was despatched to Illinois, the site of other key races, and Vice-President Dick Cheney was sent to Idaho, previously solid Republican territory where Democratic candidates are posing a threat for the first time in a decade.

Although Mr Bush has a busy schedule, Republican strategists have stressed that his stops have been chosen carefully.

"We’re focusing his energy on places where he can best turn out the vote for Republican candidates. These are all races that are close. These are all races that are likely going to come down to turnout," a senior official told the Associated Press.

For the first time in his presidency however, US press reports have noted that Mr Bush has not always been welcome on this year's campaign trail.

His personal unpopularity and, above all, widespread disapproval of the conduct of the war in Iraq has driven many Republican candidates to focus on local issues, while their Democratic counterparts have been to tar their rivals with the general disillusionment dogging the Bush Administration.

A New York Times / CBS poll released yesterday showed only 29 per cent of American voters approved of the way that Mr Bush is managing the war, while The Washington Post listed a host of races in which Republican candidates have deliberately blurred the lines of their campaign to distance themselves from the White House.

Even Senator Burns, who played host to Mr Bush last night, has put out a television advertisement in which he praises the record of Montana's Democratic senator, Max Baucus, and claimed that the Democratic candidate running for his own seat would not support Mr Baucus the way he has.

The phenomenon has run both ways, with Democrats, emboldened by unhappiness at the war in Iraq, keen to take the electoral stances that have served Republicans so well in recent years, notably on national security. "In the final ad rush, it has grown difficult to tell which candidates are Republicans and which are Democrats," the Post reported.

In one electoral district in Texas, the last-minute campaign strategy has been to play down the fact that a candidate is dead.

Glenda Dawson, a Republican congresswoman in Pearland, died in September but a campaign leaflet distributed this week shows her smiling and noting her achievements for the district and did not mention her passing.

Ms Dawson is expected to win the reliably Republican district, in which case a special election will be held in a few months time. State Representative Dennis Bonnen, who is running her campaign, denied deliberately obscuring her death.

"We don’t suggest that there’s a great thing she’s going to accomplish for the voters in the future," he said. "We had already made it clear to voters in one piece that she had passed away. We didn’t think it was necessarily necessary to repeat it."

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