I'm sure you're going to get this from them again, and there are at least two good options here:
"Isn't that what you predicted for 2004? And look how that turned out."
Or, if you really want to turn the knife :
"NO WAY! Ever since we got control of the voting boxes way back in 2000, EVERY election belongs to us."
From the brief description you've given of them, that last one is a line they've discussed at least among themselves many times as to the reason they're losing elelctions. Coming from you, it will bring them up short.
LOL. Yes, they did predict a win for Kerry and Gore too. In baseball terminology, libs are being "shut out" on predictions.
Oh, man, yeah...I can hear myself now...."name for me just ONE prediction......."