Here is the link to the Star Tribune article talking about Biden's stumping in Minnesota, a state that Dems haven't lost since 1972. http://www.startribune.com/166889946.html?refer=y
And here's a tweet from Josh Kraushaar, executive editor of The Hotline, making your same point:
Yes, a state that Dems haven't loss since
Nixon Defeated McGovern. Thanks to good campaigning/ticketing:
1976: Two words: Walter Mondale.
No chance in hell for GOP, thanks Watergate.1980: Ditto. Though a bit closer this time around.
Republicans almost maxed out in general election, though a serious blunder by Carter could've delivered the state to Reagan.1984: This time he's the Presidential candidate. And, while he was certainly no Hubert Humphrey, Mondale was pretty popular amongst the Minnesota folk.
Possible Republican victory if Reagan spent five more minutes in Minnesota.1988: Does what would've been expected in the Midwest: Shift Democratic. HOwever, Minnesota was actually trending Republican, as you can see by looking at the "Trend" map on the uselectionatlas results page for 1988.
No chance in Limbo, given Farm Crisis.1992: Bad year for Republicans, of course not going to become more Republican.
Nah, not happening. See 1976 except replace "Watergate" with "Culture Wars" and "Perot".1996: Ditto.
2000: Gore beats Bush by two points in an election that was in "tossup" mode. Not really exceptional. Meanwhile, New York, which last voted Republican in 1984, went over 60% for Gore. Just saying.
Possible Bush victory if Nader stole two more points from Gore.2004: Kerry does somewhat better without a major third party candidacy. However, considering that it's a tossup election (like 2000) the 51% victory isn't so impressive.
Possible Bush victory if he didn't go "crusadin" in part of the campaign.2008: Typical Democratic Wave year election victory. A little disappointing though when you consider that MN underperformed next to it's Upper Midwest counterparts (Wisconsin, Iowa, and Michigan). Again, MN shows obvious signs of trending R.
Possible R victory if Obama declared that he hates God and Kittens.To me Minnesota doesn't sound like it was that diehard D of a state. Merely that Democrats have won it consistently due to lucky positioning or anti-GOP wave years. 1976-1984 can be explained by Mondale. 1988 can be explained by the Farm Crisis. 1992 and 1996 can be explained by Clinton Plus Perot. 2000 and 2004 are pure tossup results. 2008 was a good Democratic year.
With all of that said, the GOP winning Minnesota could happen if Romney overperforms. Though right now I would say it's lean Obama.