"There is no way on this Earth that I would leave the good people of the Republican Party I've met prey to some of the leadership I've seen ... that is corrupt, that lacks integrity and has betrayed their best values and their best interests," said Keyes, who since joining the race for Illinois' U.S. Senate seat has trailed Obama by at least 40 points in opinion polls.
Keyes moved to Illinois from his home state of Maryland in August as a replacement candidate for Jack Ryan, who dropped from the race after sex-club allegations emerged from his divorce from actress Jeri Ryan.
"From the point of view of the things I deeply believe in to be right and necessary, Barack Obama is wrong and taking the wicked and evil position on every single one of them," Keyes told reporters after attending church services Sunday.
"I have no response to Mr. Keyes' apocalyptic, over-the-top statements. I think everyone's gotten accustomed to them," Obama said.