I believe this person would have a great shot at winning the nomination, but I do think it would put him at a disadvantage in the general election, at least when you look at the coalition that Obama has built.
He/she would get considerable swing out of the rural South, which would counteract any issues with depressed secular turnout. A libertarian R could make OR, WA and parts of New England competitive, but an Evangelical D would be very well positioned in NC, FL and GA, and no worse off than Obama in VA.