Fearless Leader
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But then there's Scoop Jackson, who could've made the Democratic nomination in the 70s. It's not just state pride on my part- he combined some of the better parts of the neoconservative movement (a staunch support for democracy around the world) with some of the better parts of the Democrat positions at the time (a strong record on civil rights, for instance). He would've strangled the neoconservative movement in the cradle- if he'd become President, guys like Wolfowitz would've stayed Democrat. And, perhaps most importantly, if he'd been President, it's entirely possible, even likely, that the Democrats could've stolen the thunder of the Reagan years- the Moral Majority would never have formed, and the Blue Dog/Jackson democrats (yeah, same Jackson) would've been satisfied with the Democrats and not seen an desire to create a coalition with the Republicans. In fact, the reverse might have been true- in short, Jackson could have been a Democrat version of Republican Ronnie- the anti-Reagan, if you will. (Of course, it could've all gone south, and he might've been a terrible President seen as too hawkish for the Democrats and too Democrat for the Republicans. But we'll never know, and I'm going to assume the best of him for now.)
I'm a big Scoop fan myself. I highly recommend reading the recent biography that came out Henry Jackson: A Life in Politics by Robert Kaufman. That being said, I think you're a bit too optimistic. The biggest barrier to a Jackson presidency would be having Jackson win the Democratic primary due to the fact that from 1968 onwards he rapidly became isolated from his own party. His views on foreign policy, especially his unflinching and unwavering support for Vietnam were an anathema to post 1968 Democrats. This coupled with his poor public speaking abilities (great 1 on 1 but horrible with a crowd), conservative social values (anti abortion, homosexuality), and his inability to truly grasp the post 1968 primary system pose significant barriers. Furthermore his views on Civil Rights were far more of the "Equality of Opportunity" stripe than the "Equality of Result" stripe that was dominating the Democratic party.
That being said I do think that given the right preparation and POD, Jackson and other conservative Democrats could do enough to stall the leftward swing of the party long enough for him to be elected in 1976 (1972 is a wash, Jackson's a nobody). But even if he wins the nomination, his poor public speaking skills and lack of youth support is going to hurt him in the election. For the first time since 1960 the GOP's going to be running a candidate with more dovish foreign policy views than the Democrats. Having Jackson win there is another longshot IMO.
But assuming that he does win the 1976 primary and then goes on to defeat Ford would he perform well enough to merit being on this list? I'm not so sure. The biggest problem with Jackson is that the man spent absolutely no time in the private sector. He had little to no grasp of economics and favored draconian wage and price controls as a means with which every economic problem could be solved. Given his stance on the economy the years of a Jackson presidency would likely be lean ones for the American people, at best you could hope that they'd be no worse than Carter's in OTL. Foreign policy wise Jackson would handle the Iran situation far differently (probably better) ditto with the Panama Canal and the Cold War in General. America would certainly feel more confident abroad with Jackson at the helm and his willingness to flex American muscle. That being said, his hawkishness could very well start WWIII.
Now would this be enough to stop Reagan? Initially I thought so, but I'm increasingly convinced that Reagan would wipe the floor with Jackson in this scenario. A struggling economy coupled with Reagan's charisma and telegenic campaign style would see Jackson crushed. Furthermore given that Jackson's and Reagan's foreign policies would be nigh identical, assuming Jackson doesn't lose the 1980 primary, there might be a strong 3rd party campaign come 1980 representing the social democratic elements of the American political spectrum.
Finally there's the issue of Jackson's health which might preclude him from running for a second term altogether. With presidential doctors the heart condition that killed him in OTL may well be discovered earlier in TTL causing him to reconsider running. Also a possibility is that the stress of being POTUS aggravates the condition leading to his premature death.
Jackson would certainly have been an interesting president, but I doubt he'd be one of the best presidents the US ever had.