Florida Democrats face a steep climb in the State House, where Republicans hold a convincing margin heading into 2010, but the wind is clearly at the Democrats’ backs as next year’s legislative races take shape.

Since 2006, Democrats have gained nine seats in the lower chamber, and conditions on the ground have produced a wealth of new targets for Democratic takeover:

Stemming chiefly from term limits, there are 25 House seats now held by Republicans where no incumbent is running, while Democrats have only three such openings. The disparity, helped along by voter trends, gives Democrats a chance to pick up – perhaps – 18 seats, [Democratic Rep. Ron] Saunders said.

Key to Saunders’ math, is even more calculus. In particular, it’s rooted in the performance of Chief Financial Officer Alex Sink in Republican-held districts during her 2006 race against then-Senate President Tom Lee, a Republican.

Across 18 districts, mostly narrowly GOP-leaning and concentrated in Central Florida, Sink gained at least 48 percent of the vote against Lee. Among them, are districts held by Reps. Pat Patterson, R-Eland, Alan Hayes, R-Umatilla, Dorothy Hukill, R-Port Orange, Ralph Poppell, R-Port Orange, Sandy Adams, R-Oviedo, Ed Homan, R-Tampa, and Bill Galvano, R-Bradenton.

In addition to the Republicans’ 25 open seats, Democrats are also buoyed by the Obama campaign’s massive voter registration effort in the state, which left the party with a 750,000-voter advantage in statewide registrations.

Even if Democrats fail to win back a majority next year, they’ll be working hard to gain as much ground as possible before 2011 redistricting.