INDIANAPOLIS—Unless citizens throughout America keep him in their thoughts, say his name to themselves over and over, and otherwise believe in him with all their might, Barack Obama may cease to exist, the candidate warned supporters Thursday.

"My fellow Americans, I am currently very strong and very, very real," Sen. Obama told a cheering crowd of 12,000 at the Indiana State Fairgrounds. "Even here in Hoosier country, a traditional Republican stronghold, your faith has kept me from growing faint, becoming transparent, and slowly fading from view."

"But please, don't stop now," Obama added. "Unless you continue to believe in me, I'll completely disappear. You have to keep me in your thoughts at all times!"

Deputy campaign manager Steve Hilde- brand, who has been tasked with making sure volunteers are chanting Obama's name with their hands clasped and their eyes shut tight, said that the candidate has nearly faded out at several points during the long campaign. Early in the primaries, when Hillary Clinton was up in the polls, Obama's typically solid composition began to waver and his voice became a distant echo. Currently the Democratic nominee is a blurred and vague outline in the state of West Virginia, where he trails McCain by almost 12 points. In Tennessee, Alabama, and Georgia, Obama is already a waning dream to some people, while in Texas, he is nothing more than a gentle wind, rustling through the trees—a ghostly visitor soon departed.

"During these last few days, I call on all Americans to keep thinking happy thoughts," Obama said. "Otherwise our dream of turning this country around will vanish, as I vanish, leaving nothing behind but a wisp of my memory and a few faint strains of my voice, forever whispering, 'Yes, we can…. Yes, we can…. Yes, we can.'"