At a Hillsborough campaign rally Wednesday, former President Bill Clinton was introduced by Charlotte Mayor Pro Tem Susan Burgess.

Burgess is North Carolina's only superdelegate committed to Sen. Hillary Rodham Clinton for the Democratic nomination. Six others are committed to Sen. Barack Obama, and some are unpledged. The superdelegates, who are party leaders and elected officials, will pick the nominee if voters don't choose a clear winner in primaries and caucuses.

Polls show Obama with a large lead among North Carolina Democrats, but Clinton's state field director Mike Trujillo said the same was true in California and Texas, where Clinton eventually won. At the rally, Bill Clinton emphasized the importance of North Carolina's May 6 primary.

"This is the biggest state still to vote," he told a crowd of several hundred on a ball field. "Your voice will resound across America."

Speaking in the home county of John and Elizabeth Edwards, Clinton noted that Mrs. Edwards favors his wife's health care plan over Obama's.

"She said Hillary's health care plan was better, and as you all know, she knows something about that issue," he said. Elizabeth Edwards has inoperable cancer.

Clinton also discussed his wife's proposals to reach energy independence and promote development of affordable hybrid cars.

"If our country can beat the world to the moon," he said, "we ought to be able to beat the world to clean coal and a car battery."

The focus on energy costs resonated, especially President Clinton's pitch for cars that can go 100 miles on a gallon.

"I'd like to have a car that'd go 100 miles per gallon," said 45-year-old Julie Terrell of Mebane. "Are they going to give us the money so we can afford the cars that go 100 miles per gallon? That would be the hard part."

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