Scoop Jackson was a Warhawk Democrat in the mid to late 20th century. He ran for President a few times - both in '72 and '76. He didn't do much work in the '76 primary and ended up not getting the nomination, allowing Jimmy Carter to win.
Carter is a frustrating figure because I feel he is a good guy, but he also ruined the best chance the Dems had at shaping the country. The Republicans should have been deeply damaged by Watergate yet somehow they were able to come back less than a decade later and hold onto the Oval Office for the longest time this side of FDR.
So I propose Scoop as an alternative. He was strong on civil rights but he also wanted to defeat the Soviets (which was Reagan's big thing).
He did die in '83, but that would still be the majority of a '76-'84 presidency. Maybe we could even have Carter then - he was at least friendly enough to Jackson to put his name in at the convention as part of the Stop McGovern movement. He could be a good analogue as a Democratic HW Bush.