WASHINGTON — Presidential debates have produced some of the most memorable moments of modern campaigns: A tanned and relaxed John Kennedy meeting a sweaty and pasty Richard Nixon in 1960. Gerald Ford denying Soviet domination of Eastern Europe in 1976. Al Gore sighing and rolling his eyes in 2000.

For all the lore and media buildup, the events haven't had much impact on election outcomes.

"Where you started the debate season is pretty much where you end the debate season," said Christopher Wlezien, a political science professor at Temple University and co-author of the book "The Timeline of Presidential Elections."