Americans elect lots of people to represent their differences, but just one to represent the union, said Wayne Fields, who is considered an expert on presidential speeches and debates.

The challenge for anyone seeking the nation's top office, Fields said, is to articulate a vision of the nation's unity.

Fields spoke at the second annual Emil C. Weis Lecture at Southeast Missouri State University Wednesday. The lecture was also part of the university's Common Hour program. Fields is author of the book "Union of Words: A History of Presidential Eloquence." He is a professor at Washington University in St. Louis.

Starting with George Washington, presidents have worked to articulate what Americans have in common. It has always been a delicate balance between the rights of the individual and the creation of a more perfect union, Fields said.

The tool to tell the story of common ground is speechmaking, a tool that dates back to the beginning of the country.

"We are deeply committed to political speech and rhetoric," Fields said. At the same time, Americans are suspicious of the spoken word. "There is a fear of seduction," he said. "We can be talked into things that go against our values and better judgment."

Against that backdrop, Fields said, presidential candidates have worked through their spoken words to tie the nation together. Over the years, presidents have relied on historic events as touchstones. First, they talked of the American Revolution, then the Civil War, and most recently the Great Depression and World War II.

However, fewer people have a personal connection to World War II or the Depression, Fields said. As a result, the country is in a state of flux. "This generation has to find something to grab hold of," he said. "Vietnam isn't it."

Americans are looking to the presidential candidates to help define the times we live in. The president represents a confluence of the times and the personality of the candidate. "It's hard to imagine Jimmy Carter or Ronald Reagan being elected at any other time in history," Fields said.