A foreign student asked me (her teacher) what THRILLA WITH VANILLA meant. I haven't the slightest idea and when I go to Google, the only reference is the Romney-Obama debate, as though the expression was just invented for this purpose. Can anyone help define this (preferably out of this political context)?
You have picked up the use by Jonah Goldberg in National Review in 2011: he seems to be suggesting an Obama-Romney debate would be dull because of Romney lacks personality. It may also suggest at least one of the individuals has white skin.
It has been used before, in the promotion of a March 2002 celebrity boxing match involving Rob Van Winkle (previously known as Vanilla Ice).
The less distorted Thrilla in Vanilla seems to be more common: for example it was used in 2009 to describe the Texas gubernatorial race, a US Senate hearing unlikely to produce disagreements and as a title of an adult film as well as being used for various food and drink concoctions.