Could Mitt Romney become the first Republican presidential nominee to win Minnesota since … Richard Nixon? Local ABC affiliate KSTP and Survey USA conducted a new poll this past week, and it shows that Barack Obama’s lead has been cut in half, and that he’s well below the 50% mark.  Has presidential politics returned to the Land of 10,000 Lakes? (via Gary Gross)

In an election for President of the United States in Minnesota today, 07/20/12, three months till voting begins, Barack Obama captures the North Star State’s 10 electoral votes, defeating Mitt Romney 46% to 40%, according to a SurveyUSA poll for KSTP-TV in Minneapolis / St. Paul.

Romney and Obama are effectively even among male voters. All of Obama’s advantage comes from female voters, where Obama leads by 14 points. Romney edges Obama among Minnesota’s Independents, but not by enough to offset Obama’s 2:1 advantage among Minnesota’s moderates. Romney leads in Northeastern MN, but Obama leads in the rest of the state.

Interestingly, the likely-voter breakout may undersample Republicans just a bit.  The D/R/I on the sample is 38/32/28, with a D+6.  In the big Democratic wave of 2008, when Obama won Minnesota by double digits, the exit polls showed a D+4 advantage, 40/36/25.  (There are no exit polls for MN from 2010.)  Democrats may well be slightly less inclined to turn out in 2012, but I’d guess that Republicans are more charged up in Minnesota than they were in 2008, and that the 32% is too low.

Obama’s performance is certainly one reason why Democrats might be less inclined to turn out, but the Senate race is another.  It’s not that they’re at risk of losing Amy Klobuchar’s grip on the seat; she leads GOP nominee Kurt Bills by 24 points, about the same gap by which she beat Mark Kennedy in the Democratic wave election of 2006.  If Bills doesn’t do something to get engaged in the media and the race, Klobuchar will win this one in a sleeper — which will not exactly fire up Democrats to run to the polls.

Republicans have two key referendums on the ballot this year, too.  Voters will choose whether to amend the state constitution to require photo-ID for voting, and whether to move the current statutory language defining marriage into a constitutional amendment.  Conservatives expect a strong turnout for support of both, and the poll shows both look likely to pass.  The marriage amendment is ahead 52/37, with majorities of both men (53/39) and women (52/36) in favor.  The voter-ID bill looks even stronger, with almost two-thirds supporting the change (65/28) and even a narrow plurality of Democrats favoring it (48/45).

If Obama can’t get to 50% in Minnesota against Romney this early in the general-election cycle, then it may be a very long election — especially when the voter turnout model has to be shaped by a non-competitive race (so far) for the US Senate seat held by a Democratic incumbent and two popular conservative referendums.