The “Hope Express” has travelled 2,537 miles to more than 40 cities across the flat Midwestern landscape of Minnesota with a candidate who, at every stop, talks about his passion for change, ending the rancour of politics and “reaching out across the aisle”.

To a casual observer, it is hard to tell that Senator Norm Coleman is a Republican seeking re-election after spending much of the past six years aggressively backing war in Iraq and defending the White House. His posters, speeches and campaign literature make no reference to his party affiliation, President Bush or John McCain.

But these are desperate times for the Republican Party and Mr Coleman shows little embarrassment about taking a leaf - or lifting a large sheaf - from the Barack Obama playbook. No one should have “a monopoly on the word ‘hope’,” he tells The Times outside the Bear Lodge log cabin restaurant in Brainerd.

He admits that his chances of holding the seat in Democratic-leaning Minnesota rely on persuading voters to split their support between him and Mr Obama. “This is a state where independents play a big part. If all you get is your base, you lose.” The four-letter word “lose” looms larger than “hope” for Republican incumbents such as Mr Coleman on November 4, when voters will pick more than just a new president.

Democrats have an outside chance of winning the ten Senate seats they need, including that of Mr Coleman, to secure unfettered power on Capitol Hill for the first time since 1965.

They already control the House of Representatives with a majority of 235 to 199 - and hope to pick up as many as two dozen more seats. Targets in Minnesota include Michelle Bach-mann, who made headlines last week by calling an investigation into “antiAmerican” activities of Democrats. Her opponent, the wonderfully named Elwyn Tinklenberg, is surging in polls and has received $800,000 (£490,000) in donations since this outburst.

But it is in the Senate that Democrats are working hardest to strengthen their position. Two years ago they won a narrow 51-to49 majority that includes the independent Democrat Joe Lieberman, who is campaigning actively for Mr McCain this year.

Time and again legislation has been blocked by an arcane procedure known as the filibuster in which 41 senators can endlessly delay a debate coming to a vote simply by continuing to talk. To overcome it, the Democrats must have at least 60 seats.

Republicans, who are defending 23 of the 35 seats being contested, give warning about the prospect of a high-spending liberal “super-majority” with a stranglehold on both Congress and the White House. Party strategists have already written off Virginia and New Mexico, acknowledge that they may well lose Colorado, Alaska, New Hampshire, Oregon and North Carolina, and hint at retreat in the battle to oust Mary Landrieu in Louisiana. All eyes are now turning to a third tranche of targets: Kentucky, Mississippi, possibly Georgia, and Minnesota.

Mr Coleman’s opponent in this state is, even by the admission of some his own aides, “not the perfect candidate”. Al Franken, a television comedian who once branded all Republicans as “shameless d***s” and wrote an erotic article for Playboy called “Porn-o-Rama” in which he fantasised about having sex with machines, has sometimes struggled to repackage himself as a candidate for that most sober of legislatures: the Senate.

Outside his rally for 2,000 people in Minneapolis on Tuesday night, a group of student Republicans held placards reading: “No Franken Way” or “Potty Mouth Al”.

Inside, he received the blessing of Hillary Clinton, who appeared all too aware of the dangers of a comedian politician. “He will stand up, sometimes with that smile of his and sometimes with one of those jokes – that may or may not be funny – but he will stand up for you,” she said.

She could not resist making reference to his support for her husband during the 1990s, praising Mr Franken for “taking on the ‘vast right-wing conspiracy’ before other people even admitted it existed”. She added: “Unless we get the 60 votes in the Senate, we won’t end the Bush era and we will continue to be frustrated by the rearguard action of the Republicans. Al Franken, with your help, can be the 60th vote we need.”

Mr Franken limited himself to some tepid jokes about Mrs Clinton’s age and the need for supporters with his bumper stickers not to cut up other drivers before polling day. He has returned to his roots in Minnesota to fight this election but, like other celebrities turned politicians, sometimes he seems to perform a role he has rehearsed too often in front of a mirror. “Let’s get to work! Let’s get to work! Let’s get to work!” he screamed at the end of his speech.

The crowd, reflecting the progressive metropolitan tendencies of Minneapolis, lapped it all up. Speeches were littered with rousing calls not only to win the filibuster-proof majority in the Senate but also to capture the White House. Mr Franken’s posters boldly proclaim himself as a “Democrat for US Senate”.

In the more conservative rural areas of Minnesota, such hyper-partisanship strikes a jarring note. This is a state where Jesse Ventura, a former wrestler, became Governor ten years ago and Dean Barkley, his campaign manager, has made the Senate election a three-way race by picking up about 20 per cent support in polls.

Back in Brainerd, Mr Coleman walks slowly around the restaurant speaking softly to the 100 or so diners gathered to see him. He gently makes his conservative case against gun control, a big issue for hunters, and expresses admiration for troops and small businesses.

“I know you, you know me,” he says. “People want change, a change in tone and change in getting results. I’ve been one of the forces pushing for the right kinds of change.” Recently he announced a high-minded and self-denying ordinance under which he would no longer run negative advertising against Mr Franken. “My advisers tell me I’ll lose by doing this but I feel so much better. I’m now so proud of my campaign,” he says.

This causes Democrats to splutter in rage because the National Republican Senate Campaign continues to brand Mr Franken as “unfit for office” every night on TV and Mr Coleman himself shares a house with Jeff Larson, whose company is being paid to produce an endless stream of automated telephone calls against their opponents.

Mr Coleman, however, is revelling in his new Obama-esque persona. “My wife got up this morning to find terrible graffiti on our garage door - horrible words. You know there is too much vitriol out there. Americans are better than that. We’re better than that,” he tells the diners. “Hope can conquer fear.”

Among his audience is Evie Smith, who confesses that she is voting for Mr Obama but will back the Republican senator. “I was undecided until I saw Mr Coleman but I like what he has done by stopping these negative ads,” she says.

The special needs teacher could never vote for Mr Franken because “some things he has done in the past, they crossed the line”. Where did she learn about him? “From TV”. You mean negative adverts? “Maybe.”

Outside the restaurant Mr Coleman says he believes that both the Obama and McCain campaigns should learn from his decision to run a positive campaign. “My message to both sides is that we will all be better if we don’t lower the level,” he says, flashing a smile of improbably white teeth.

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