The Ohio plumber, whose real name is Samuel Wurzelbacher, became famous after he was referred to constantly in the final presidential debate. McCain has been portraying the plumber as emblematic of people with concerns about Obama's tax plans.
Wurzelbacher on Tuesday also agreed with a McCain supporter who asked him if he believed "a vote for Obama is a vote for the death of Israel."
"I'll go ahead and agree with you on that,"
Wurzelbacher told the man, retired Florida lawyer Stan Chapman, who was visiting Ohio.
Wurzelbacher was joined at the rally by Rob Portman, a former Ohio congressman and budget director under President George W. Bush, who said he disagreed with Chapman's assessment of Obama's foreign policy.
Wurzelbacher himself has undercut the Republican message about him by revealing his income is less than earlier suggested, which means he actually stands to fare better under Obama's tax plan. But Wurzelbacher says Obama's plan would hurt him if he were able to buy the plumbing business from his current employer.
Wurzelbacher's first trip to the podium was without notes. He often apologised to reporters gathered in a flag store for talking from his gut.
"I'm honestly scared for America," Wurzelbacher said.
He later said Obama would end the democracy that the US military had defended during wars.
"I love America. I hope it remains a democracy, not a socialist society. ... If you look at spreading the wealth, that's honestly right out of Karl Marx's mouth," Wurzelbacher said.
Wurzelbacher was scheduled to make stops in other towns in Ohio, an important swing state. The bus tour included guests billed as Mary the Flag Lady, Mike the Painter and Linda the Fitness Trainer.
