Unusual Presidential Elections

[Nym90]

All valid points, and another reason why Nixon's margin was so large was because of Watergate. Having copies of your opponent's campaign plan certainly doesn't hurt.
McGovern was not as extreme as he was made out to be. The man had been a war hero during World War II and been elected to the Senate from a conservative state (South Dakota). A large part of why he was able to be made to look like a fool was because of the fact that Nixon knew his every move in advance.

[Nym90]

Well John Anderson helped Reagan to win the state in 1980, and it still very narrowly went for Reagan that year by less than 0.2%. And in 1984, it was the 2nd-most Democratic state in the nation behind Mondale's home state of Minnesota. But yes, Massachusetts did swing a little more Republican in the 80's than it had been before, and than it has been since. Even Massachusetts native Dukakis only carried it by 8 percent in 1988, but it really started to become much more Democratic under Clinton. In 1984, Massachusetts was only about 15 percentage points more Democratic than the national average, rather than almost 30 points more Democratic like it is now.
But yes, 1980 especially was somewhat of an aberration in Massachusetts, as it was only the 7th most Democratic state in the nation that year, after usually being one of the 2 most Democratic along with Rhode Island for most of the last 40 years. The Massachusetts economy may have been especially hard hit by the recession that year, and Carter seems to not have been nearly as popular (relatively speaking) in Massachusetts and other Northeastern states as other Democratic nominees have been in the last 40 years, while on the other hand performing better in the South in both of his runs than any other Democrat in the last 40 years has.
Carter was an abberation in many respects, as the voting patterns during both of his runs represented somewhat of a return to the old pre-Civil Rights Act voting patterns, at least geographically speaking.
And yes, it is somewhat odd that McGovern won Massachusetts by 8 points, but lost Rhode Island, when both states have otherwise voted very similarly to each other throughout the years, except in 1980, when Carter was much stronger in Rhode Island than in Massachusetts. My theory is that Massachusetts voters are more liberal than those in Rhode Island, especially culturally, and thus were more likely to support McGovern, but Rhode Island has more "traditional" Democrats (the state is heavily Catholic, with Catholics that seem more devout than those in Massachusetts) who were more attracted to Carter. Rhode Island is just as Democratic if not slightly moreso than Massachusetts, but seems less liberal.

[Nym90]

Well, Dave has done the math...http://www.uselectionatlas.org/USPRESIDENT/GENERAL/pe1968whatif.html

Although it's worth noting that his "No Electoral Majority" What-If isn't the "best" possible one. At least in my opinion, no disrespect intended on your hard work Dave ;-). It relies on a faithless Nixon elector in North Carolina still casting his ballot for Wallace even though in this case it costs Nixon the election (which this elector probably would not have done), and besides, only Missouri and Ohio are required for Humphrey to win rather than Missouri, New Jersey, and Alaska (which requires a greater percentage shift to Humphrey in Alaska than would be required in Ohio).