More than 60 million people are expected to watch when the nationally televised, 90-minute debate kicks off at 6 p.m. PST, far more than watched the two major party national conventions and dwarfing the number that watched Romney in Republican primary debates.
Underscoring the significance, the men will arrive at the University of Denver debate site after days of closed-door rehearsals, Obama in Nevada and Romney in Colorado. The stakes are particularly high for Romney, the former Massachusetts governor who's stayed close to Obama in most polls but continues to trail, having struggled to find momentum.
"It's one of the few possible game changers left for him, and the only one he has a certain amount of control over," said Tobe Berkovitz, an associate professor of advertising at Boston University.
Most polls show Obama remains vulnerable -- his Gallup job approval rating Sept. 28-30 was 47 percent, about where it's been for some time, and a Quinnipiac Polling Institute survey released Tuesday, taken Sept. 25-30, put him ahead of Romney 49 percent to 45 percent.
But the early autumn Republican reviews in for Romney's campaign are not pretty.
In some states, candidates who share the Nov. 6 ballot with the former Massachusetts governor already have taken steps to establish independence from him. Party strategists predict more will follow, perhaps as soon as next week, unless Romney can dispel fears that he is headed for defeat despite the weak economy that works against Obama's prospects.
Former Mississippi Gov. Haley Barbour, who headed the Republican Party when it won control of Congress in the 1990s, said disapprovingly over the weekend that Romney's campaign has been focusing on polling, political process and campaign management.
Matthew Dowd, who was a senior political adviser to President George W. Bush, said the Romney campaign was almost guilty of political malpractice over the summer and during the two political conventions.
Ed Gillespie, a senior adviser to Romney, defended the campaign in a conference call with reporters on Monday. "Our message is very clear, which is we cannot afford four more years like the last four years," he said.
Republicans say there is time for Romney to steady his campaign but only if he acts quickly.
Obama also faces high expectations. Regardless of political spin from the campaigns, Americans by a 2-to-1 margin expect Obama to win the debate, according to polls. Romney has not engaged in a one-on-one political debate since he ran for governor of Massachusetts 10 years ago, while Obama debated Republican John McCain three times in 2008 and is a familiar presence on American television.
The numbers suggest an opportunity for Romney, who will try to tell voters that Obama should be held responsible for a stubbornly sluggish economy. Romney plans to stress that Obama's remedies too often involve "going forward with a stagnant, government-centered economy," said senior adviser Ed Gillespie.
Obama is trying to lower those expectations. "The president is familiar with his own loquaciousness and his tendency to give long, substantive answers," said Obama campaign spokeswoman Jen Psaki, calling it a challenge when there's a timer running.
"Governor Romney, he's a good debater. I'm just OK," Obama said with a grin to a Nevada audience earlier this week. "But what I'm most concerned about is having a serious discussion about what we need to do to keep the country growing and restore security for hardworking Americans."
Barring a major gaffe or surprise, few analysts expect the debate to radically change the race right away. Quinnipiac found that 86 percent thought it would make no difference in how they voted.
But what a debate can do is plant images and ideas with voters that they'll seek to confirm or dismiss over the campaign's final month.
The key economic flash points Wednesday are expected to involve taxes, the federal debt and jobs.
Romney is running ads tying Obama to the government's $16 trillion debt, notably in a recent spot showing a baby and talking about the debt she was inheriting.
Obama has pointed out that Romney's plans would mean even more debt.
Obama's predecessor, President George W. Bush, was responsible for a huge chunk of the debt boom. When he took office in 2001, the figure was $5.7 trillion. Because of tax cuts, a new Medicare drug program, war spending and other factors, the debt was $10.6 trillion when he left office eight years later.
Both Obama and Romney would add trillions more to the debt over the coming decade.
On jobs, Romney is expected to offer frequent reminders that the jobless rate went over 8 percent during Obama's first full month in office in February 2009 and has never dropped below that level. That's the longest stretch over 8 percent since such records started 64 years ago.
The nation lost about 7.9 million jobs during the December 2007-June 2009 recession -- most of which occurred during the Bush administration -- but the pace of hiring has since lagged behind usual post-recession standards.
Obama is likely to tout his American Jobs Act, which would provide government spending on public works projects as well as incentives for business that would help create millions of jobs.
Obama and Romney are scheduled to debate again Oct. 16 and 22. Vice President Joe Biden and the Republican nominee, Rep. Paul Ryan of Wisconsin, will debate Oct. 11.
Information from the Associated Press was included in this report.
I.D. law overturned
HARRISBURG, Pa. -- Pennsylvania voters won't have to show photo identification to cast ballots on Election Day, a judge said Tuesday in a ruling on the state's controversial voter ID law that could help President Barack Obama in a presidential battleground state.
Commonwealth Court Judge Robert Simpson delayed Pennsylvania's voter ID requirement from taking effect this election, saying he wasn't sure the state had made it possible for voters to easily get IDs before Nov. 6.
Gov. Tom Corbett, who had championed the law, said he was leaning against an appeal.
CHARLOTTE, N.C. -- Vice President Joe Biden said Tuesday that the middle class has been "buried" during the past four years, a statement that Republicans immediately seized upon as an unwitting indictment of the Obama administration.
Republican presidential candidate Mitt Romney replied on Twitter that he agrees with Biden, saying: "the middle class has been buried the last 4 years ..."
Biden told about 1,000 people in Charlotte that Romney would cut taxes for millionaires and raise them for middle-class families. "How they can justify raising taxes on a middle class that has been buried the last four years?" Biden said. Lis Smith, a spokeswoman for Obama's campaign, said the Republican response to Biden's remarks was "another desperate and out-of-context attack."
HENDERSON, Nev. -- Forget about a date night. President Barack Obama and wife Michelle will be marking their wedding anniversary with a debate night.
The couple's 20th anniversary is Wednesday. "Go figure," the first lady said recently. The two have planned a belated anniversary celebration on Saturday.
Stewart, O'Reilly ready to 'Rumble'
One is from Fox News, the other Comedy Central. But despite their opposing sides on the political spectrum, something almost like -- gasp! -- friendship has evolved between Bill O'Reilly and Jon Stewart.
On Saturday, the two will square off in a mock debate in Washington, D.C., to be streamed online for $4.95, with half the proceeds going to charity.
The event has been dubbed "The Rumble in the Air-Conditioned Auditorium."
From Herald news services
More Nation & World Headlines
Experts determine that wing piece is from missing 777 GOP debate lineup: Trump and Bush in, Fiorina and Perry out Bipartisan investigation cites management flaws at IRS Civilian casualties in Afghanistan hit highest number since 2009, U.N. says Aides to Ron Paulís 2012 presidential campaign indicted Family of man shot dead by police on Skid Row files lawsuit 400 migrants saved from wreck off Libya, 25 bodies found Economists dump on Trump boast to bring jobs back from China
Our new comment system is not supported in IE 7. Please upgrade your browser here.