* Obama has chance to spell out his economic approach
* Hard act to follow after Clinton at Democratic convention
* Final night moved indoors after weather threat
By John Whitesides
CHARLOTTE, N.C., Sept 6 (Reuters) - President Barack Obama delivers his argument for re-election on Thursday in a high-stakes closing act at the Democratic National Convention that will spell out his approach to revitalizing the stumbling U.S. economy.
Obama will accept the party's presidential nomination in a much smaller venue than planned, the 20,000-seat Time Warner Cable Arena, after the threat of severe weather forced a move from a 74,000-seat outdoor football stadium.
He will have a tough act to follow in President Bill Clinton, who confronted challenger Mitt Romney and his Republican allies on Wednesday in a detailed attack that ignited the arena.
Obama, under pressure to tell Americans how he will create jobs, will lay out his vision for a second White House term in a nationally televised address watched by tens of millions of people. It was scheduled to begin shortly after 10 p.m. EDT (0200 GMT on Friday).
"The president now has an opportunity to talk about how we lift the country, how we rebuild the middle class, the things we have to do together to achieve the kind of future that people are looking for," senior adviser David Axelrod said on MSNBC.
Vice President Joe Biden will also speak on the final night of a three-day convention that marks the start of the fall campaign season, with the two White House contenders locked in a tight race.
Asked during a New Hampshire campaign stop whether he would watch Obama's speech, Romney first answered: "Don't plan on it," but later said he would love to watch if he thought his opponent would give a report on earlier promises he made.
Clinton galvanized Democrats on Wednesday with a hearty defense of Obama's efforts to repair the economic "mess" inflicted by what Clinton said were misguided Republican policies of deregulation and huge tax cuts for the wealthy.
Despite earning rave reviews from political pundits, Clinton's television audience was restricted by the National Football League's opening game, which drew 21 million viewers on NBC. Clinton attracted nearly 20 million viewers on cable networks and the other broadcast networks.
On Tuesday night, an address by first lady Michelle Obama that portrayed her husband's understanding of the struggles of everyday Americans energized the convention and lit up social media.
'TELLING A STORY'
"These speeches are all of a piece. We're telling a story here," senior adviser David Plouffe said on NBC's "Today" show.
"I think President Clinton laid out very powerfully the president's record and the choice in this election," he said.
Obama and Romney have been running roughly even in polls before the Nov. 6 election as Obama struggles to make his case for re-election amid a tepid economic recovery and persistent high unemployment of 8.3 percent.
An online Reuters/Ipsos poll on Thursday gave Romney a 1-point edge on Obama, 45 percent to 44 percent, slightly down from his 2-point advantage on Wednesday.
Obama has trailed Romney, the former Massachusetts governor who emphasizes his business background as head of a private equity fund, in many polls on the question of who would best handle the economy.
But Plouffe played down expectations for a big boost in polls from the Democratic gathering.
"We think we're making a lot of progress this week, but again you're not going to see big bounces in this election," Plouffe said on ABC's "Good Morning America." "I think for the next 61 days it's going to remain tight as a tick."
The switch in venue for the acceptance speech froze out tens of thousands of Obama supporters who had planned to attend the stadium speech, although watch parties were being organized nationally and around the convention in Charlotte, North Carolina.
"If we had started seeing severe thunderstorms and lightning, in particular, it would have been a problem," Obama told some of the supporters in a conference call on Thursday afternoon. "And we would have had a situation where we were putting you guys at risk."
The party faithful lucky enough to still have tickets for Obama's speech started arriving at the arena more than 10 hours before he was due to speak. The early arrivals were treated to a sound check by singer James Taylor and celebrity sightings such as actresses Ashley Judd and Tyne Daly.
Convention officials planned to retain most of Thursday night's schedule, including musical acts like the Foo Fighters and James Taylor, although Earth, Wind & Fire will not perform in the smaller space.
Former U.S. Representative Gabrielle Giffords of Arizona, wounded in a 2011 shooting, will lead the Pledge of Allegiance on Thursday, Roll Call reported.
Clinton set the stage for Obama with an address that directly responded to Republican questions about whether Americans are better off than they were when Obama took office.
"No president - not me or anyone before me - no one could have fully repaired all the damage that he found in just four years," Clinton said of the economy Obama inherited from Republican President George W. Bush.
"But conditions are improving, and if you'll renew the president's contract you will feel it," he said.
The speech was vintage Clinton as he frequently left the prepared text for digressions on topics including George Washington's false teeth. His attacks on Romney were made more effective by his praise for other Republicans including Bush and former President Ronald Reagan.
Democrats were embarrassed on Wednesday when they were forced to revise their policy platform after it was approved by delegates to reintroduce language that mentioned God and named Jerusalem as Israel's capital.
Dropping the Jerusalem wording had upset Jewish supporters and annoyed Obama, who ordered it put back in the platform, mostly a symbolic document.