No matter what President Obama says Thursday night when he accepts his party’s nomination, there will be no Greek columns — and no balloon drop.

With forecasters expecting severe thunderstorms to roll through Charlotte on Thursday night, convention officials scrapped plans to have Obama speak from outdoors at the 73,000-seat Bank of America Stadium, opting instead to keep delegates at the indoor Time Warner Cable Arena, with room for about 15,000.

Ahead of the speech, campaign aides remained tight-lipped about the specifics of Obama’s speech, but senior Democrats urged him to keep focused on the economy, the chief concern among voters.

“He doesn’t have to give a State of the Union, but he has to connect with some emotional clarity to let people know where we’re going in this economy,” said John Podesta, who served as chief of staff to President Bill Clinton and is now chair and counselor of the Center for American Progress, a think tank closely associated with the Obama administration.

Obama has been criticized, at times, for being overly cool in settings that call for more emotion. Chicago Mayor Rahm Emanuel, Obama’s first White House chief of staff, warned that this speech — Obama’s second accepting his party’s nomination for president – must be “a visionary piece with big goals set out for the country.”

“It’s got to be somewhat of the road map we will take, but not the 10-point plan,” Emanuel said at a breakfast meeting hosted by The Washington Post and Bloomberg News. “That’s not what it’s going to be; it shouldn’t be that. And I think it would be a mistake if it was that.”

Obama campaign spokeswoman Jennifer Psaki said the threat of thunderstorms Thursday night might have forced organizers to quickly evacuate the stadium, home to the National Football League’s Carolina Panthers.

Republicans insisted that the change of venue was driven less by weather concerns than worries that Obama would be unable to fill the stadium. But Psaki and other Democrats retorted that 65,000 people had tickets to attend, in addition to about 6,000 official delegates, thousands of reporters and 19,000 people on a waiting list – more than enough to top the stadium’s seating capacity.

In addition to giving up the dramatic outdoor venue, the convention will end without the traditional balloon drop, because organizers said they had not made plans to fill the indoor arena with balloons.

Brad Woodhouse, spokesman for the Democratic Party, told The Post that by abandoning the stadium the campaign will also miss the chance to mine the larger crowd for new voters and campaign volunteers.

Many supporters didn’t learn the news until told by reporters Wednesday afternoon.

Everlene Baker came with friends from Palm Beach County, Fla., and had tickets only for the Thursday night speech. Now, she said, “I can watch it on TV in the hotel room.”

Matt Paine and his wife, Delia, came from Bend, Ore., to sell homemade campaign buttons. They hoped another football stadium speech would reenergize Obama’s supporters the way his 2008 address in Denver had.

“There’s no question that the enthusiasm is down from 2008,” Paine said, noting that he has sold fewer buttons this year than he did four years ago. “I think anyone will tell you that 2012 is not 2008 and nothing will be 2008 again. That just doesn’t happen like more than once a century.”

Diviniah Payne-Shantefiere, 58, a delegate slated to attend Obama’s speech, said: “He should go to the various venues and make the rounds. He has to make a physical appearance. People came a long way and went through a lot of stuff to get here for him.”

Scott Wilson, Kevin Merida and Chris Cillizza contributed to this report.