Democrats' hopes of holding on to their Senate seat in Florida appear to be looking up, with a new Washington Post poll showing Sen. Bill Nelson (D) holding a 14-point lead on Rep. Connie Mack (R) among likely voters, 54 percent to 40 percent.

Sen. Bill Nelson (D-Fla.). (Ricky Carioti -The Washington Post)

Nelson, who also leads by 18 points among registered voters, holds a strong edge among basically all the key swing demographics, including among independents (55-37), moderates (65-25) and in the Tampa Bay (56-41) area of the crucial Interstate-4 corridor. At the other end of the corridor near Orlando, Nelson is at 49 percent, while Mack is at 43 percent -- a margin that is within the margin of error.

Nelson also wins more Republicans (15 percent) and voters who chose Sen. John McCain (R-Ariz.) in the 2008 presidential race (18 percent) than Mack wins among Democrats (4 percent) and 2008 supporters of President Obama (11 percent).

The poll is the latest showing of a key Senate race that is trending toward Democrats.

While Mack was able to close the gap during the summer and even led in some polls, four polls this month have shown Nelson building a double-digit lead: an automated SurveyUSA poll, an NBC News/Marist College poll, a Fox News poll and, last week, a Mason-Dixon poll that had Nelson leading 48 percent to 40 percent.

Democrats have also made gains in close races in Massachusetts, Virginia and Wisconsin. And in another Washington Post poll today, Democrats were asserting a double-digit lead in Ohio.

But whatever shift has happened in the national electoral counting, the poll of Florida suggests that the shift in that state is more about the two candidates. Nelson has strong numbers at 55 percent favorable and 33 percent unfavorable, but Mack is underwater at 41 percent favorable and 45 percent unfavorable.

Nelson, like Democratic Sen. Sherrod Brown of Ohio, has long been considered a second-tier GOP target this cycle. Though Florida is a swing state, Republicans continue to have problems recruiting strong candidates against the two-term senator.