Obama arrives at Democratic convention ahead of Bill Clinton's speech

President Obama arrived in the Tar Heel State Wednesday afternoon, one day before delivering his convention address.

Earlier in the day the Democratic National Convention Committee announced a venue change to Obama's big night. Rather than speaking at a football stadium in front of 74,000 people, due to weather concerns the DNCC moved the president's primetime address Thursday to the indoor basketball arena -- which seats far fewer people.

The campaign was disappointed in the decision to downgrade the audience count. " This is not a call we wanted to make. We were very much looking forward to full, energized crowd in stadium," Obama campaign spokesperson Jen Psaki told reporters Wednesday. Dispelling any rumors that the decision was made because the campaign couldn't fill the 74,000 seats, Psaki insisted the decision was made for security reasons. "It's not a game. It's a security event. Criteria ensuring no safety at risk," she told reporters on Air Force One.

A senior campaign aide to Obama tells Fox News that his acceptance speech is "substantially done."

"He may tweak a word or two here or there," the aide told Fox News, adding that the president is still doing "run-throughs" and tends to "make adjustments" during them.

Obama watched his wife, first lady Michelle Obama, address the convention Tuesday night from the White House with his daughters. Ahead of the first lady's big night, he told supporters at a campaign event Tuesday that he would try not to get emotional during Michelle's remarks.

"And I'm going to try not to let them see their daddy cry, because when Michelle starts talking I start getting all misty," he said.

Former president Bill Clinton will headline the convention Wednesday night, a day before Democrats formally nominate Obama for a second term. The Obama campaign was careful in selecting Clinton for this roll, trying to capitalize on the former president's popularity and remind voters a Democrat was in office the last time there was a budget surplus.

The Republicans will be ready to pounce on the former president.

"My guess is we'll get a great rendition of how good things were in the 1990s but we're not going to hear much about how things have been the last four years," Mitt Romney's running mate, Paul Ryan, said at a campaign event in Iowa.

Clinton had yet to finish writing his speech as of Wednesday morning, according to senior aides to the Obama-Biden campaign. In addition to speaking on the economy, Fox News confirms president Clinton will also clarify some of the attacks from the Romney-Ryan campaign regarding welfare reform.

"As the original author of the reform, he has a very acute perspective on the debate that's happening now," an Obama campaign aide told Fox News.

Fox News' Wendell Goler and James Rosen contributed to this report.