1980 Kennedy vs Reagan would likely end up with this reuslt
Reagan 428 53%
Kennedy 110 45%
Anderson 0 2%
Kennedy would do better in New England, Worse in the South,
Kennedy best time to run was 1976
I agree on the south, he would have gotten killed there but I disagree on everything else. Hear me out first
Victory was possible for the Dems in 1980 regardless of how bad things were. Carter led the polls for a majority of the election even while being so inept and clumsy campaigning. See here:
https://uselectionatlas.org/FORUM/index.php?topic=115543.0Reagan had a lead in the summer but Carter came back around the middle of August/labor day and lead until midway thru October. Reagan started to out-campaign him and then the debate came and Reagan powned him all over. After that Carter was starting to become DOA, and then on election weekend when the iran thing failed to work out people decided they were done with him and went with Reagan.
The Dems would have had a chance if they were more competent during that election span and more importantly more united. They still might not have won but they would have done much respectable. He would have without a doubt ran a much better campaign than Carter did he wouldn't have been so pitiful or had the "woe is me" vibe Carter did in some of his ads. Getting rid of the Carter spectre was what would have made or broke Teddy. I think he could have done it but it would have been as tough as what McCain went through in 2008.
Here's some scenarios with pretty colors:
Minus giving him Cali I think this was Ted's best chance of barely making it. Getting Ohio in this scenario would elect him.
This would maybe be his biggest possible win. NH/VT/ME was heavily Republican then (while to be fair the Dems won ME in '68 so I see it going more than those two,) Cali would have been harder for him to win so that's maybe the biggest stretch.
I say this would be his most respectable loss give or take Iowa/NJ.
Odds are he would have conceded the south in turn for the Mid West and Pacific states. He wouldn't win the bible belt but I can see him getting the liberal states (ie Wisconsin/Michigan,) and playing hardest for Cali, Ohio, Illinois, Pennsylvania, and New Jersey. He could win without Cali but he need all 4 of those states to stand a chance. Winning wouldn't have been easy but he could have done it in a perfect situation.