(Corrects day of week in first and seventh paragraphs)
* President makes no mention of "47 percent" theme
* Obama avoids signature attack lines of campaign
* President wasn't looking at "checklist of attack lines"
By Samuel P. Jacobs
WASHINGTON, Oct 4 (Reuters) - During their 90-minute debate on Wednesday night, President Barack Obama talked four minutes longer than Republican challenger Mitt Romney. But when the debate was over, it was what Obama didn't say that defined the evening - and helped make it a good one for Romney.
In a debate that largely was a mix of campaign talking points and tedious policy detail, the themes that Obama's campaign have emphasized to drive down Romney's approval ratings did not surface.
Obama did not mention Romney's work at Bain Capital, the private equity firm whose role in sending thousands of jobs overseas has been cited by Obama's campaign as it has portrayed Romney as a job-killer.
Obama resisted chiding Romney about the former Massachusetts governor's reluctance to release more than two years of his income taxes. Democrats have questioned whether Romney - who has a fortune estimated at up to $250 million - is hiding something about his finances and why he keeps millions of dollars in offshore accounts.
But Obama's most startling omission was not uttering a phrase that has dominated the campaign for much of the past two weeks: "47 percent."
That would be the percentage of Americans who Romney - speaking at a private fundraiser that was secretly videotaped in May - said were "victims" who are dependent upon government benefits and are unlikely to vote for him.
The video of Romney's remarks, which surfaced last month, was a benchmark in the campaign. Last week, Obama's team released an ad featuring Romney's "47 percent" comment in seven key states, including Colorado, the host of Wednesday's debate.
Many voters say that Romney's comments had given them a negative opinion of the former Massachusetts governor.
Nearly six in 10 people said in a Reuters/Ipsos poll released last month that they felt Romney unfairly dismissed almost half of Americans as victims.
In the fallout from the video, Obama's small lead over Romney in nationwide polls increased by a few points. Meanwhile, Republicans campaigning in tight U.S. House and Senate races across the country tried to distance themselves from Romney's remarks.
So it was widely expected that Obama would remind voters of the Romney video at Wednesday's debate, which was projected to draw a national television audience of about 60 million viewers.
Moderator Jim Lehrer appeared to invite Obama to do just that during one of the debate's final segments.
"Do you believe there's a fundamental difference between the two of you as to how you view the mission of the federal government?" Lehrer asked.
"The federal government has the capacity to help open up opportunity and create ladders of opportunity and to create frameworks where the American people can succeed," Obama said.
Obama campaign advisers defended the president's response.
"The president wasn't looking at a checklist of attack lines. He was trying to explain his plans," said Obama campaign spokesman Jen Psaki.
Romney supporters said that Obama's avoidance of the topics that could have put Romney on defense might signal a shift in strategy by the president's team.
"It could be that the Obama folks don't feel it's a good vehicle for them anymore," said Romney senior adviser Kevin Madden.
Obama also mostly held his tongue when it came to an accomplishment that Vice President Joe Biden has said should be among the top reasons to re-elect Obama: The successful mission by U.S. forces that killed Osama bin Laden.
In a debate that focused on domestic policy, Obama made no mention of the mastermind of the Sept. 11, 2001, attacks until the closing minutes of the debate.
In wrapping up the debate, Obama again avoided the anti-Romney themes that have been hallmarks of his campaign.
Instead, Obama acknowledged there were areas in which he had fallen short as president.
"You know, four years ago, I said that I'm not a perfect man and I wouldn't be a perfect president," Obama said. "And that's probably a promise that Governor Romney thinks I've kept." (Additional reporting by John Whitesides in Denver; Editing by David Lindsey and Jim Loney)