U.S. President Barack Obama is in Charlotte, North Carolina for the Democratic National Convention, a gathering of his staunchest supporters he hopes will propel him to re-election to a second term in the White House.

Mr. Obama arrived in the southern state Wednesday afternoon. Hours earlier, party officials looked at Thursday's weather forecast and decided to move his night-time nomination acceptance address from an outdoor football stadium because of concerns about rain. The president will instead speak in a much smaller, 20,000-seat indoor arena where the remainder of the convention is being staged.

Democratic officials said they feared the possibility of rainstorms during the speech. Mr. Obama's Republican opponents said the real worry for his supporters was that the president might not attract enough people to fill the 74,000-seat stadium.

In a statement, convention organizer Steve Kerrigan said the group shared the “disappointment of over 65,000 people” who had signed up for credentials to attend the outdoor event. He said Mr. Obama would speak to them during a Thursday conference call.

Meanwhile, former U.S. president Bill Clinton takes the spotlight at the convention on Wednesday, adding more high-profile support for Mr. Obama's re-election.

Mr. Clinton, the 42nd American president, will formally place the 44th president's name up for nomination during a nationally televised address. The relationship between the two Democrats has improved in the years since Mr. Obama defeated the former president's wife, Hillary Clinton, in the 2008 party nomination campaign.

Mr. Clinton remains a popular figure among many Americans who recall the economic prosperity during his two terms in office in the 1990s, and analysts say he could help Mr. Obama win support from older, white working-class Americans.

The highlight of the convention's opening night Tuesday was a speech by first lady Michelle Obama, who talked about her husband's character and ability to make tough political choices.

“Barack refused to listen to all those folks who told him to leave health reform for another day, another president. He didn't care whether it was the easy thing to do politically — that's not how he was raised –he cared that it was the right thing to do.”

Democrats used their opening speeches reaching out to women voters, with Mrs. Obama recounting how the president's early background — and his grandmother's employment setbacks — helped shape his governing policies as president.

Mr. Obama's opponent in the November 6 election is Republican Mitt Romney, a one-time venture capitalist and former governor of Massachusetts. Surveys of voters show the two candidates in a virtual tie nine weeks ahead of election day.