With four days to go, John McCain and Barack Obama's campaigns are at full-throttle, making their final pushes for undecided voters as the presidential race headed into its final weekend.

McCain continued his attack on Obama Friday, saying the Democratic candidate's economic policies were pulled from the far left of American politics.

Obama "began his campaign in the liberal left lane of politics and has never left it," McCain said in Hanoverton, Ohio. "He's more liberal than a senator who calls himself a socialist," he added, referring to independent Vermont Sen. Bernie Sanders.

McCain, who polls show is trailing Obama in the race for the White House, said his own policies are more towards the centre.

"He (Obama) wants to raise people's taxes -- that's clear," McCain said earlier Friday on ABC's "Good Morning America."

U.S. Congressman Donald Payne, who is working on the Obama campaign, said the economy is, without question, the focus of this election.

"The McCain campaign wanted homeland security, Iraq and foreign affairs to be the number one issue however the financial situation in the United States has certainly overridden that tremendously," Payne told CTV.

Obama maintains he will not impose any tax increases on families making less than US$250,000 a year and individuals pulling in less than US$200,000 annually. He continued stressing his key message that McCain has not been independent from the Bush administration when it comes to the economy.

" . . . when it comes to the economy, when it comes to the central issue of this election, the plain truth is that John McCain has stood with President Bush every step of the way," Obama said at a rally in Des Moines, Iowa. "I mean, he hasn't been a maverick, he's been a sidekick."

Undecideds

As voters prepare to cast their ballots next Tuesday, an Associated Press-Yahoo News poll of likely voters put the Democrat ahead, 51 to 43, with a margin of error of plus or minus three percentage points.

The same poll shows some Americans are still undecided. According to the results, one in seven (14 per cent) can't decide or they back a candidate but may switch.

The voters in question are described as more likely to be white and less likely to be liberal. They also disproportionately backed Hillary Clinton's failed bid for the Democratic nomination, say researchers.

To expand his reach to these undecideds, Obama is moving state to state this weekend through to Monday in ones that voted for George W. Bush in 2004.

"What you started here in Iowa has swept the nation," he told several thousand gatherers in Des Moines. His victory in the Iowa's Democratic caucuses on Jan. 3 set in motion his drive to winning the party's nomination.

Weekend blitz

Both candidates have scheduled a weekend blitz of campaigning in a final effort to sway voters, especially in key battleground states.

McCain is spending his second straight day in Ohio Friday, where aides say he must win to have a chance at taking the White House.

"We're closing, my friends, and we're going to win in Ohio. We're a few points down but we're coming back and we're coming back strong," he said Friday.

Ohio supported Bush in the last election and has voted with the winner in each presidential election for two decades.

McCain released a new television ad in which he pledged to fix the economy, cut government waste and safeguard the country's security.

"I've served my country since I was 17 years old. And spent five years longing for her shores. I came home dedicated to a cause greater than my own," said McCain, a former navy pilot who was imprisoned and tortured for more than five years as a Vietnam prisoner of war.

On Saturday, McCain will detour from battleground states for an appearance on "Saturday Night Live."

He is then expected to head West to his home state of Arizona.

A recent poll from McCain's home state shows him in a statistical dead heat with Obama.

He told his supporters to expect more attacks on him from the McCain camp.

"More of the slash and burn, say-anything, do-anything politics that's calculated to divide and distract; to tear us apart instead of bringing us together," Obama said in prepared remarks.

Obama said he admired a presidential candidate who said in 2000, "I will not take the low road to the highest office in this land."

"Those words were spoken eight years ago by my opponent, John McCain," Obama said. "But the high road didn't lead him to the White House then, so this time, he decided to take a different route."

The Illinois senator is next scheduled to return to his Chicago home later Friday to see his kids for Halloween. After that, he'll head to a rally in Gary, Ind.

Obama will then go West, where he hopes to pull enough voters to win Colorado on Tuesday.

Payne said the weekend is going to be "very, very exciting" with a heavy schedule not only for the candidates but also for surrogates in every state.

"I've never seen anything like this in my many years in politics," Payne said.

While Obama has the lead in most polling, both nationally and in key states, Payne said their team is not taking anything for granted.

"We're cautiously optimistic but even in our meetings into late last night no one is conceding this race and there is no question that many of the battleground states are still close which means they could go either way," Payne said.

"So this is not what we call a slam dunk, this is going to be a tough fought battle up to the very end."

Interesting developments in the campaign:

  • Obama said Friday on CNN that the economy and energy independence would be his top priorities if he's elected president. Health care reform and tax cuts for the middle class came in at number three and four. Number five would be reforming the education system.
  • Ken Duberstein, former chief of staff for Ronald Reagan, told CNN this week he intends to vote for Obama. He said he was influenced by another former Reagan official: Colin Powell.
  • Another prominent Republican has offered a frank assessment of Sarah Palin's capacity to handle the presidency should such a scenario come to pass. Lawrence Eagleburger, a former Republican Secretary of State and one of John McCain's most prominent supporters, said the Alaska governor is unprepared to take over the job on a moment's notice. He added that even after some time in office, she would only amount to an "adequate" commander in chief.
  • Al Gore will be making campaign stops in Florida Friday for Obama. He told a rally in West Palm beach that Florida may again determine the outcome of this election.

With files from The Associated Press