Had Scoop Jackson won the 1976 RAT presidential nomination, Ford probably would have won the general. No way that Scoop would have won 11 of the 13 Southern states like Carter did (MS, AL, TX, TN, KY and NC probably would have gone to Ford, as would OH); remember, when Kerry got 47% in FL in 2004, he became the first Northern Democrat to get over 45% in a Southern state since Kennedy in 1960. And the only Ford states that I can see Scoop picking up are WA and OR.
I'm not so sure. There really was a huge anti-GOP backlash in the South post-Watergate. Even with Northwesterner Jackson as the standard bearer (and likely he would've chosen a Southerner for balance, either Carter, Govs. Wallace or Reubin Askew), I think he would've stood an excellent chance of winning and carrying a number of Southern states (my TN was going Democrat regardless, and they took out Sen. Bill Brock, too, who was painted as a dishonest Nixon crony). I also believe Jackson would've done much better in the Western states (including CA, which only went to Ford by 1.78%), enough for a win.
By all accounts, Carter should've won by a wider margin, but Ford was already rapidly closing on him at the end of the campaign (had it been held a week or two later, that might've been all that Ford needed to get Ohio, and the election, in the bag). Jackson, who was ultra-popular in Washington State and got grossly disproportionate votes as a Democrat, might've played far better overall than Carter (if anything, Carter's Southerness cost him in close races, and also Ford did better than he should've given the national climate in Northern states).
^This was Ford-Carter.
^I think with Jackson/Askew vs. Ford/Dole, it would've looked like this. You may vehemently disagree, but the only state I think Ford would've picked up under this scenario would've been Mississippi, and perhaps not even that. It would've been a landslide for the Dems, even if TX went to Ford.