Not having seen the episode of The Daily Show in question,
might I be right in guessing that you mean this?
( flake has nothing against your right leg, Fri 13 May 2011, 2:21, 1 reply)

Yup, that's the one.
Also found here.

Stewart suggested that maybe Santorum should change his last name to Lemonparty. ("Go ahead and Google- I'll wait...")
( The Resident Loon Not a demographic. Do not measure., Fri 13 May 2011, 2:38, closed)

You sir
are just plain wrong. Wrong.

I am never going to be able to scrape that image from my brain now.
(dchurch bah, Fri 13 May 2011, 7:13, closed)

What, Lemonparty?
Sheesh, I thought everyone in here would know what that one is! Sorry. It's one of the classic internet shock images, along with Tubgirl and Goatse. Apologies for exposing you to your first viewing of it- but I suppose I can kinda pass the blame on to Jon Stewart, as it was him that I was quoting with the suggestion to search for it. (Imagine being responsible for thousands upon thousands of people being exposed to both santorum and lemonparty in one sitting...)
( The Resident Loon Not a demographic. Do not measure., Fri 13 May 2011, 16:03, closed)

I can imagine it.
And I'm sporting wood as a result.
( flake has nothing against your right leg, Sat 14 May 2011, 0:56, closed)

I myself
have goatse'd entire message boards in the past by telling them to NOT look it up as they'd regret it.

I have to confess, the resultant torrent of horrified abuse hurled at me filled me with a warm glow of pride.
( The Resident Loon Not a demographic. Do not measure., Sat 14 May 2011, 20:07, closed)

I
have a really piss-poor memory. I remember tubgirl (nearly made my lodger sick when I showed him that only last week), and goatse; but Lemonparty - whilst I had a vague recollection of having looked it up in the past, I couldn't remember, so bloody did it again!
(dchurch bah, Tue 17 May 2011, 7:20, closed)