Barack Obama was today preparing to deliver his “closing argument” for the presidency in the crucial battleground state of Ohio as his epic battle with Republican John McCain entered its final week, seeking to tie his rival once and for all to the failed economic policies of President Bush.

The Democratic nominee will declare that his opponent has campaigned for 21 months without telling voters how he would differ from the president in his handling of the economy. With his speech in Canton, deep in America’s industrial heartland, Mr Obama hopes to seal the deal with the small-town, blue-collar voters who will decide the election, as polls show him edging ahead in the state and a number of other demographically similar battlegrounds.

Mr McCain is to hold a competing rally in neighbouring Pennsylvania, after vowing to make a comeback even as national and state polls showed his path to victory growing ever steeper. The twin visits to the industrial northwest follow a weekend in which the two rivals blitzed western states leaning towards Mr Obama, with Mr McCain hoping to make up lost ground by painting his rival as a socialist in favour of dramatic wealth redistribution.

Aides to Mr Obama said he would urge voters to choose "hope over fear, unity over division” as he summed up the long presidential race. The 47-year-old Illinois senator is widely favoured in the polls as best qualified to stop America’s accelerating economic decline, sentiment that has seen him make substantial inroads into traditional Republican territory.

“In his speech, Senator Obama will tell voters that after 21 months and three debates, Senator McCain still has not been able to tell the American people a single major thing he’d do differently from George Bush when it comes to the economy,” a campaign statement said.

With campaign coffers overflowing after unprecedented fundraising success, Mr Obama was to follow up his Ohio speech with a 30-minute advertisement airing on national networks at huge expense on Wednesday evening.

State-by-state polling suggests he is now near or above the 270 electoral votes needed to become the first African-American president. Mr McCain has pointed to some surveys which show his rival's national lead dwindling but this has not been reflected in the electoral college, which apportions electoral votes to states based on their population.

An ABC News-Washington Post national poll gave Mr Obama a 52-45 per cent lead over Mr McCain among likely voters, down from his 54-43 percent margin last week.

"We've closed in the last week and if we continue this close in the next week you're going to be up very late on election night," the Republican told NBC.

But in reality Mr McCain's electoral map is shrinking as he battles to hold on to states won by President Bush in 2004, such as Iowa, where yesterday he sought to portray himself as the scrappy underdog unbowed by an arrogant and power-drunk rival.

The 72-year-old former Navy pilot told supporters he relished the fight and repeated his contentious claim that the Democratic nominee had already drafted his inauguration speech.

"What America needs now is someone who'll finish the race before starting the victory lap, not for himself but for his country," he said.

The Republican sought to distance himself from the Bush administration, argued that he had always had major differences with the president on issues such as climate change and government spending.

"Do we share a common philosophy of the Republican Party? Of course," he said, in a remark later seized on by Mr Obama to buttress his case that the pair had long marched in step.

"But I stood up against my party, not just President Bush but others as well, and I have the scars to prove it," the Arizona senator added.

At a 100,000-strong rally in Denver, in the traditionally red state of Colorado, Mr Obama leapt upon Mr McCain's statement. “We know what the Bush-McCain philosophy looks like," he said. “It’s a philosophy that says we should give more and more to millionaires and billionaires and hope that it trickles down.”

Meanwhile Mr McCain argued that voters should elect him president to create a check on a Democratic Congress that he says is determined to increase taxes and the size of government.

“That’s what’s going to happen if the Democrats have total control of Washington,” he said, speaking of higher taxes and a bloated federal bureaucracy. “We can’t let that happen.”

He then moved on to two rallies in Ohio, a state that voted for President Bush in 2000 and 2004 and has become vastly important for both candidates because it could guarantee Mr Obama’s victory. Since Abraham Lincoln was elected in 1860, no Republican has ever won the presidency without carrying Ohio, where voters have selected the eventual winner in the past 11 presidential elections.

A poll by Ohio’s eight largest newspapers now shows Mr Obama leading Mr McCain there by three percentage points, 49-46. Last month, the poll showed Mr McCain with a six-point lead.

In a further blow to Mr McCain, the largest newspaper in Alaska, where his running mate Sarah Palin is governor, yesterday endorsed Mr Obama. Mrs Palin was campaigning over the weekend in Florida, another key battleground where the two tickets are locked in a dead heat.

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