Republicansought to raise doubts about his rival's tax policies and readiness to be commander in chief as he fought desperately to stem losses in traditionally Republican-leaning states on the next-to-last weekend of the testy presidential race.
Both campaigns focused on western states Saturday. Once reliable Republican territory, much of the West has seen its politics and demographics shift over the last decade as the Hispanic population, which tends to favor Democrats, has grown.
Three states considered still in play to varying degrees - Nevada, Colorado and New Mexico - could be vital if the electoral math gets tight.
Despite his close ties to the region, the Arizona senator trails in the polls in these states, forcing him to spend precious time in an area he once hoped to have wrapped up by now, reports CBS News correspondent Chip Reid. But McCain pledged a scrappy close to the campaign.
"We're a few points down and the pundits, of course, as they have four or five times, have written us off," he told a rally of about 1,500 supporters in Albuquerque, New Mexico. "We've got them just where we want them. We like being the underdog."
A Newsweek poll of registered voters showed Obama with 53 percent to McCain's 40 percent. The poll found Obama leading in every age group and among men as well as women, and even holding a slim 46-to-44 percent edge among working-class whites.
The telephone poll, conducted from Oct. 22-23 with a margin of error of 3.6 percentage points, also found that 62 percent of those surveyed have a favorable view of Obama.
Obama needs to run "like he is behind," CBS News consultant and Democratic strategist Dee Dee Myers said on the Early Show Saturday, adding that the Obama campaign should "focus on winning 270 electoral votes - not 350."
"They've done a fantastic job, the Obama campaign, in expanding the electoral map in creating more avenues to winning," said Myers. "But they don't need to try to run the board here."
Myers said the key for the Obama campaign in the campaign's final days is to focus on states like Florida, Ohio, Virginia - and the Western states like Nevada, New Mexico, and Colorado where Obama and McCain now campaigning.
On Saturday, Obama mocked his Republican rival for recently trying to distance himself from the unpopular President George W. Bush.
Speaking at a baseball stadium in the toss-up state of Nevada, Obama said it is too late for McCain to say that Bush let the economy get out of whack.
"John McCain attacking George Bush for his out-of-hand economic policy is like Dick Cheney attacking George Bush for his go-it-alone foreign policy," Obama told supporters at the rally in Reno, Nevada.
The Democrat, who will campaign in Colorado Sunday, put aside political events on Thursday night and Friday to spend time with his grandmother in Hawaii, whom he described as gravely ill.
Obama's emphasis is on getting supporters to vote early - locking in votes that might not materialize if people get busy or stay home because of bad weather on Election Day, Nov. 4.
He plans to spend the next two days in the West, heading to new Mexico and Colorado on Sunday, reports CBS News correspondent Dean Reynolds. Obama will then head east where he will be joined on Wednesday by the only democrat who can rival him as a campaigner - former President Bill Clinton.
McCain, pivoting from his three stops in Colorado on Friday, was also pushing hard in New Mexico on Saturday. He held a rally in Albuquerque and was later heading to Mesilla, farther south.
The Republican candidate heads to Iowa on Sunday, looking to make up for some lost ground in a Midwestern state his campaign aides argue is closer than the public polling shows. His running mate, Alaska Gov. Sarah Palin, was in Iowa on Saturday.
Obama, a senator from Illinois, unveiled a two-minute TV ad that asks, "Will our country be better off four years from now?"
"At this defining moment in our history, the question is not, 'Are you better off than you were four years ago?"' Obama says in the ad. "We all know the answer to that." Without mentioning McCain, the ad promotes Obama's economic policies while saying that Obama will work to end "mindless partisanship" and "divisiveness."
The length of the ad, which will start airing in key states Sunday, highlights Obama's fundraising superiority - most campaign commercials run 30 seconds or a minute - and the Democrat was far outspending McCain on television advertising.
The Republican National Committee, meanwhile, released a TV ad Saturday questioning whether Obama has the experience to be president. The ad, featuring the image of a stormy ocean, says the nation is in "uncertain times" that could get worse and asks whether voters want a president "who's untested at the helm."
As the collapsing economy consumes voter attention, McCain has seized a line of attack that Obama is poised to deepen the problem by raising taxes.
Seeking to energize his backers, McCain said Obama was "more interested in controlling wealth than creating it."
"He believes in redistributing wealth," McCain told supporters at his Albuquerque rally. "We've seen that movie before in other countries. That's not America."
"There's a lot of volatility left, particularly with these undecided voters in battleground states," CBS News analyst and former Bush advisor Dan Bartlett said on the Early Show.
"What John McCain has to try to do, and obviously he has a tougher hill to climb, is to keep hitting this issue of taxes and try to raise fresh doubts here at the last minute that at this time in our country's history, we don't need to be entrusting somebody with so little experience at the national level," Bartlett said.
He added: "He's going to hammer home that message over the next few days and then hope that maybe Barack Obama trips up or acts a little too presumptuous that this might be over and give an opportunity here at the close to make -- to shake things up."
Obama counters that he would lower taxes for most wage-earners and that McCain's tax plan favors wealthy corporations.
Obama's running mate,, campaigned Saturday in Suffolk, Virginia, where he said McCain is out of touch on economic issues. Polls show the southern state is leaning toward Obama who is trying to become the first Democratic presidential candidate to win Virginia since President Lyndon B. Johnson in 1964.
Biden also criticized Palin's remark in North Carolina that she likes campaigning in "pro-American" regions of the country and a McCain adviser's recent comment that the more rural parts of the state are the "real Virginia."
"We are one nation, under God, indivisible. We are all Americans," Biden said, growing louder with each word as the crowd cheered.
While campaigning Saturday in Sioux City, Iowa, McCain's running mate,, said her criticism of Obama isn't negative or mean-spirited.
"Don't be made to feel guilty. I'm not feeling guilty," said Palin, the Alaska governor.
While she spoke, cries of "he's a socialist" rang out from crowd.
Polls show the path to the winning tally of 270 electoral votes is tricky for McCain, a Republican weighed down by the economic crisis and an unpopular incumbent president.
The meltdown in financial markets and the national economic downturn have helped undermine McCain's standing in the polls because Obama is viewed more favorably than McCain on handling economic issues.
The economy has almost eclipsed foreign issues such as the wars in Iraq and Afghanistan with voters, and putting McCain, a former prisoner of war in Vietnam whose strength had been considered his foreign policy experience, at a disadvantage.
New surveys have shown Obama's lead growing in key battleground states such as Ohio and Pennsylvania. The winner of the U.S. election is not determined by the popular vote, but instead by a state-by-state tally of electoral votes, making certain states key to a Nov. 4 victory.
Obama, wary of overconfidence among his backers, is charting multiple winning paths.
That's where 19 electoral votes in three closely contested Western states factor into the equation.
Nevada, with five votes, is posing the toughest challenge for Obama; the race is a tossup. Colorado is competitive, though Obama has a slight edge in polls in the state that offers nine votes. Obama is more deeply favored to win New Mexico's five votes.
President Bush carried all three states in 2004. Obama is focusing his time on plucking away states Bush won four years ago while McCain is playing defense.
Obama could win the White House by hanging onto all the states that Sen. John Kerry won four years ago and then sweeping the three Western states getting attention this weekend.
However, McCain has mounted comebacks before, such as last year when his campaign seemed all but over even before the first primaries. But political momentum can change fast, and McCain was able to regroup and eventually become the nominee.
Part of the West's demographic change includes larger numbers of Hispanics, a traditionally Democratic-leaning group that has posed a challenge for McCain. The most recent Gallup poll showed Obama leading among registered Hispanic voters, 61 percent to 29 percent.