A poll by the U.S. Chamber of Commerce shows the Florida 13th Congressional District special election still too close to call.

A mid-February poll commissioned by the Chamber shows the Republican with a two-point advantage over Democrat Alex Sink — 44 to 42 percent — well within the margin of error of +/- 4.9 percentage points. The national pro-business group gave more than $800,000 in support of David Jolly so far in the campaign.

An earlier Tampa Bay Times/Bay News 9/WUSF Public Media poll, also conducted in mid-February had Sink with the same 42 percent, but showed Jolly behind by 7 points.

This makes voter turnout the determining factor in the race to replace GOP U.S. Rep. C.W. Rep. Bill Young, whose death in October opened a seat safely held for four decades.

However, due to changing demographics, President Barack Obama carried Pinellas County twice.

Now with more than 75,000 mail-in votes already cast, Republicans account for 42 percent of the returned ballots, with Democrats making up 39 percent.

A 3-point gap, which roughly aligns with the overall voter registration rates, could be favorable to Sink. Traditionally, Florida Republicans receive an absentee voting advantage. Such was the case in the 2012 election cycle.

The Chamber is one of eight groups spending more than six figures in the CD 13 race leading up to the March 11 special election.

Outside spending has reached more than $5.5 million, according to Scott Bland of the National Journal; millions more will be coming in the next few weeks.

Fabrizio, Lee, and Associates based in Fort Lauderdale conducted the Chamber poll, measuring 400 likely voters from February 17-18.