Latino decisions been at it for a while now. See
http://www.latinodecisions.com/blog/2010/11/15/proving-the-exit-polls-wrong-harry-reid-did-win-over-90-of-the-latino-vote/Where they argued that exit polls showing Sharron Angle in 2010 NV Senate race won around 30% of the Latino vote are wrong that that her share of the Latino vote was in the single digits.
Not saying they are wrong but clearly this is an organization with an agenda of increasing the relative power of Latino interests within the Dem party arguing that the Latino share of the Dem vote is higher than what exit polls imply and with it the relative clout of Latino pressure groups in Dem power structure should increase as well.
If they are right then of course then GOP share of white vote is even larger than the exit poll suggest.