Taegan Goddard presents state level evidence of the Gallup likely voter anomaly.

"Ohio: Kerry 50%, Bush 41% (Gallup, registered voters)
Ohio: Kerry 48%, Bush 46% (Gallup, likely voters) "

The Gallup likely voter filter tosses more Democrat supporters than Republican supporters. This is true of all likely voter filters and true of actual voting compared to polls of registered voters. However, the the effect of the Gallup likely voter filter is large or in this case huge.