Could Mitt Romney be riding a preference cascade in Florida that includes Hispanic voters?   A new survey  shows Barack Obama’s support rapidly eroding in a key Democratic constituency — and this isn’t a Republican internal poll, either:

An exclusive Tampa Bay Times/Bay News 9 statewide poll shows many Hispanic voters dropping their support for Obama.

Last month, 52 percent of Hispanic voters polled said they would vote for the president. That has now dropped to 44 percent.

Romney picked up some ground among Hispanics, from 43 percent to 46 percent. And the number of undecided Hispanic voters has doubled from 5 to 10 percent.

Here’s the graphic from the TB Times, which shows the dramatic shift:

A caveat is in order.  The report doesn’t include the poll data, so we can’t see the modeling, and it also doesn’t include the top-line number — which I assume the TB Times wants to hold for tomorrow.  However, the poll comes from the respected Mason-Dixon polling firm, which means that this is no GOP-consultancy push poll, and has to be taken with some seriousness.

That makes this very bad news for Obama.  It’s possible for Mitt Romney to win Florida without winning Hispanics, but it’s got to be nearly impossible for a Democrat to do it.  And a nine-point drop in one poll series is a very significant change, especially in a single month.  With this kind of movement in this demographic, I’m assuming that Mason-Dixon will be reporting something pretty positive for Mitt Romney, who has had leads in the latest Florida polling this month.

And that prompts another question — if indeed Hispanics are moving away from Obama in Florida, what are they doing in other states?