SANTA FE, United States (AFP) - Democratic presidential candidate Senator John Kerry (news - web sites) hailed actor Christopher Reeve "America's hero," and vowed to keep up the campaign for stem cell research championed by the man known best as "Superman." In a statement released here, Kerry said he considered Reeve, who died Sunday nine years after being paralyzed from the neck down, a friend. "He was an inspiration to all of us and gave hope to millions of Americans who are counting on the life-saving cures that science and research can provide. "He met every challenge with a courage...