Florida Sen. Bill Nelson falls short of the 50 percent mark against five potential Republican opponents, according to a poll commissioned by Ron Sachs Communications and conducted by Mason-Dixon Polling and Research.

The survey, which was shared exclusively with POLITICO, shows former Gov. Jeb Bush as the most powerful Republican challenger for Nelson. Bush leads the senator by 8 points, 49 percent to 41 percent.

But Bush is not considered likely to run, and the polling memo notes that a challenge from the former governor is a “bullet [Nelson] will likely get to dodge.”

That means the Democrat will face off against a Republican who lacks Bush’s high profile and statewide popularity, such as Rep. Connie Mack, former Sen. George LeMieux, state Senate President Mike Haridopolos or former state House Majority Leader Adam Hasner.

Nelson fared better against all four of those candidates in the Sachs/Mason-Dixon poll, though he failed to win a majority of the vote in any match-up.

The closest race would be between Nelson and Mack, whose father – Connie Mack III – Nelson replaced in the Senate. Nelson would have just a 5-point advantage over Mack, leading 45 percent to 40 percent.

Against LeMieux, Nelson’s lead widens to 14 points — he’s ahead 49 percent to 35 percent. Nelson has a 23-point lead over Haridopolo (48 percent to 25 percent), and a 22-point lead over Hasner (46 percent to 22 percent).

The poll was taken from Feb. 9-10 and tested 625 registered voters.

If former Florida Governor Jewb Bush EVER wanted to re-enter the political arena, this is the race. It is Jeb’s for the taking.

If Jeb declines, then I would consider his political career over.