No Greens or Libertarians have ever been elected to US Congress.

There's a former folk singer who was on the Colbert Report who became a Democratic Representative in '06. Can't remember the name, though.

And the former singer for Orleans got into the senate too, didn't he?

I believe that HM and Ibram are referring to the same individual: Rep. John Hall of New York, who was a guitarist and songwriter for Orleans.