Time for another whodunit, or more accurately, whatdunit in this presidential election.  Two months ago, Quinnipiac gave Barack Obama a statistically significant if not entirely comfortable seven-point lead in the key swing state of Florida at 49/42.  Now, after two months of Bain attacks, gay marriage flip-flops, a visa to the daughter of Cuban dictator Raul Castro, and a weakening economy, the same pollster puts Mitt Romney up by six, 47/41.

I’ll put my money on a Murder on the Orient Express explanation:

Gov. Mitt Romney holds a 47 – 41 percent lead over President Barack Obama in Florida, where 63 percent of voters say the president’s support of same-sex marriage will not affect their vote, according to a Quinnipiac University poll released today. Another 25 – 11 percent of voters, including 23 – 9 percent among independent voters, say Obama’s support of gay marriage makes them less likely to support his candidacy.

Adding Florida U.S. Sen. Marco Rubio to the GOP ticket would give the Republican Romney/Rubio team a 49 – 41 percent lead over President Obama and Vice President Joe Biden.

Romney’s lead in the horse race compares to a 44 – 43 percent tie in a May 3 survey by the independent Quinnipiac (KWIN-uh-pe-ack) University and a 49 – 42 percent Obama lead March 28.

Florida registered voters say 52 – 44 percent that the president does not deserve a second term in the Oval Office and by 52 – 44 percent give him a thumbs-down on his job approval.

Call this an all-of-the-above effect.  If a campaign wanted to deploy a deliberate strategy of alienation in Florida, it’s difficult to see how it could have been crafted any more effectively.  Retirees in Florida who already mistrust Obama on ObamaCare can’t have been terribly pleased to hear attacks on private equity, since many of them either worked in finance or have their investments built on funds driven by private-equity firms.  His flip-flop on same-sex marriage might play well in the Northeast and West Coast, but it’s likely to hurt him in the South, and that does culturally include Florida, especially in the north end of the state.  Inviting Mariela Castro to come to the US to lecture us on politics would just be icing on the cake with the Cuban expatriate community, which organizes and votes in strength in the Sunshine State.

The internals look pretty bleak for Obama.  The gender gap plays entirely to Romney’s advantage.  Obama only edges Romney among women 45/44, but Romney wins men 50/37.  Obama also only edges Romney among Hispanics 42/40, perhaps from the fallout over the Castro visa.  Independents give Romney an eight-point edge, and even worse, only 36% vote for the incumbent.

Don’t forget, too, that the March result was a bit of an outlier in this series.  Romney and Obama were in virtual ties in January, with Romney up 46/43 and tied 45/45 in two polls that month.  Three week ago, Romney was up one point.  Florida looks to have shifted significantly in three weeks, and that could be fatal to Obama’s re-election hopes.