Why did they only publish the results for Republicans? Southern Democrats were the ones fighting the civil rights movement, so I assume number was higher.
Because it was a survey of 400 Mississippi Republicans that was mostly about the Republican primary? 2011 Southern Democrats would probably not oppose interracial marriage by a larger margin.
I googled and was unable to find a similar poll question, but I would expect it to get asked now. However, considering the 2008 primary results that gave Barack Obama (the product of an interracial marriage)
a majority of voters were at least were willing to vote for an interracial president.
If it helps, you may want to look in to the "Civil Rights Movement" and "Dixiecrats." Let me know if you need any help with your research, and be sure to report back on your findings.
Tootles!