I noticed this thread recently, and I think Wallace would win a landslide by sweeping the Midwest and the South, with the Northeast and West within reach.
Just because from 2012 someone seems detestable doesn't mean they didn't have serious star power as a candidate; even Hunter S. Thompson noted that Wallace was unique of the 1972 Democratic nominees in that he had real (scarily so) appeal. Carter was poised to win a landslide after the convention but squandered it because he ran a shitty campaign and Ford ran a brilliant one. Wallace is a lot better at playing the Washington Outsider fiddle, and will probably get a landslide.
The problem isn't just that he seems detestable from our vantage point; the problem is that he was seen as detestable from the vantage point of 1976 as well. Eight years is a long time in politics, but Democrats aren't going to be very likely to forgive and forget 1968 when he cost them the election against Nixon. (He did, too. Look a the polling. Every time Wallace drops, HHH gains while Nixon stays more or less steady.)
Yes, he showed that he had appeal throughout the country in 1964, 1968, and 1972. But 1976 is a different creature altogether. The concerns that led to whatever success Wallace had in those three years (busing and desegregation, namely) are not going to carry over to post-Watergate America, especially the Democratic Party at the time.Also note that in 1968 Wallace's support among blue-collar northerners was decimated by a targeted campaign by the AFL-CIO to remind their members of how antagonistic he was toward unions. That's going to carry over into the primaries as well.
Finally, remember why Carter won the nomination and the presidency. It wasn't just his "outsider" status; he ran on his integrity. No one in 1976 is going to mistake George Wallace for that same picture of integrity given that some of the rampant corruption he took part in in Alabama will almost certainly come to light. This will be the case even, or especially, if he changes his position on race relations. He's not going to have hippies to rail against anymore, really. Most of the people he badmouthed in 1968 are voters in 1976. The elements of social-upheaval and law & order won't be nearly as potent as they were in 1968 and 1972. Without those issues, what's his appeal to a national audience? Zero.
So there's three reasons why he would be despicable in 1976. 1) 1968 cost him the support of the party establishment, which IOTL he never won back; 2) his unpopular stances on unions and race relations are going to cost him dearly with Democratic primary voters outside of the South; 3) his national campaign will be defined by his Nixon-esque quest for power over the past two decades rather than integrity, and he won't even be able to change the topic to the topics where he would win because, in point of fact, nobody cared about them anymore.