(Reuters) - Forecasts of thunderstorms put a crimp on U.S. President Barack Obama's nomination party, forcing Democrats on Wednesday to move his planned acceptance speech from a 74,000-seat outdoor football stadium to a much smaller indoor venue.
The shift to the Time Warner Cable Arena was a setback for Obama, who hoped to create a visual spectacle in Charlotte's Bank of America stadium on Thursday to rival his 2008 acceptance speech in a football stadium in Denver.
It was also a letdown for tens of thousands of Obama supporters from around the country who had been given tickets to the biggest speech in his campaign for the November 6 election against Republican rival Mitt Romney.
Weather forecasters predicted a chance of thunderstorms on Thursday night in Charlotte, which has been battered by heavy evening rains for the last few days.
Obama volunteers Honora Price and Gayle Fleming were leaving Arlington, Virginia, to drive to Charlotte when they saw a television news ticker announcing the venue change.
"Will I be disappointed? Of course I'll be disappointed. But I've seen Obama a lot of times. So we'll be in Charlotte and we'll make the best of it," Fleming said.
Obama and the Democrats kicked off their convention with a high-energy night on Tuesday that featured an impassioned speech by first lady Michelle Obama, who portrayed her husband as a man who had lived through and understood the struggles of everyday Americans.
The address fired up Democrats, who on Wednesday will hear from the party's most popular elder statesman, former President Bill Clinton. He will try to build on the momentum of the first night with a reminder to voters of the economic good times he led in the White House.
Republicans were quick to put their own spin on the venue change, questioning whether Democrats were having trouble filling the seats in the stadium, home to the NFL's Carolina Panthers.
"Suddenly Team Obama is moving inside after questions about enthusiasm for the event. What's the real forecast for the speech? Forty percent chance of lies and scattered excuses," Republican National Committee spokeswoman Kirsten Kukowski said.
Obama campaign officials denied they had struggled to fill the seats, saying they could not risk the possibility of having to evacuate the open-air stadium in the event of thunderstorms.
"We're all disappointed because we had 65,000 ticket holders plus 19,000 people who were on the waiting list, ready and excited and fired up to hear the president deliver his speech," campaign spokeswoman Jen Psaki said.
"We know that Mother Nature doesn't always cooperate, unfortunately. We wish she did," she said.
Both parties have now been forced to adjust their convention programs because of weather. Tropical Storm Isaac disrupted Romney's Republican nominating convention last week in Florida, forcing him to cancel one day of the planned four-day gathering.
Obama's shift to the indoor arena that holds about 20,000 people will be costly. Democrats had a $5 million budget for the stadium event. Obama will speak to supporters who had tickets for the stadium on a conference call on Thursday afternoon.
One convention delegate said the smaller confines could be an advantage.
"I think it's going to be electrifying," said James Mitchell, 45, of Detroit. "Sometimes smaller venues create an energy and an intensity that is going to be over the top."
Obama arrived in Charlotte on Wednesday afternoon, but White House officials would not say whether he would visit the convention hall for the evening session. Clinton's speech highlights a night that will conclude with Obama's nomination for a second term.
"He's going to make the case for Barack Obama," Chicago Mayor Rahm Emanuel, Obama's former chief of staff and a former Clinton aide, told CBS's "This Morning."
He said Clinton will remind voters of "who we are as a party and why that matters to the middle class and people who are struggling." The two share the "same values, same policies, same goals," Emanuel said.
Clinton's high approval ratings, and voter nostalgia for the budget surpluses and job growth he produced during two terms as president in the 1990s, have made him a valuable asset despite a sometimes rocky relationship after Obama's bitter 2008 primary battle with Clinton's wife, former first lady Hillary Clinton.
Bill Clinton has already appeared in an ad for Obama in which he argues Romney would take the country back to Republican policies of deregulation and tax cuts for the rich "that got us in trouble in the first place."
Obama is eager to align himself with Clinton's economic successes and benefit from Clinton's appeal to white working-class voters who have been slow to warm up to Obama.
An online Reuters/Ipsos poll on Wednesday gave Romney a slight edge over Obama among likely voters, 46 percent to 44 percent, barely changed from Romney's 1-point advantage on Tuesday. The two contenders have been running close in national polls for months.
Early television viewing figures showed the audience for the first lady's address was about 11.1 million on the three U.S. free-to-air networks. That was in line with those who tuned in last week to hear Ann Romney speak about her husband, Mitt.
In social media, reaction to Michelle Obama's speech was off the charts.
She racked up 28,000 tweets per minute at the conclusion of her speech, according to Twitter. That was double the 14,000 that Romney saw in his convention speech last week. Ann Romney's tweets per minute tally was just over 6,000.