Alan Grayson, a Democratic congressman in Florida, is alleged to be assisting Peg Dunmire, a third candidate, in order to protect his seat from a challenge by Daniel Webster, a Republican.
One of the founders of the Florida "Tea Party", which Ms. Dunmire represents, has business connections with Mr. Grayson, and his son has worked as an intern for the congressman.
Mr. Grayson described claims he was involved with the third party as conspiracy theories. "The same people that believe that believe Barack Obama was born in Kenya," he told CNN.
Meanwhile two Democratic officials in Michigan have resigned after being linked to an apparently bogus tea party.
Michael Steele, the chairman of the Republican National Committee, accused Democrats of running dirty tricks in an attempt to salvage seats they were about to lose.
"Stop your perpetrating," Mr. Steele said in a speech in Florida. "Stop your faking. Stop your pretending.
"Mr. Grayson, you are no friend of the tea party. And therefore all these little fake tea parties that he's supporting need to step it down, step away, and step out of the way."
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