Independent voters and party switchers are providing the edge for Democrat Bill Nelson as he maintains his lead over Republican challenger Connie Mack in the U.S. Senate race, according to a new Miami Herald/El Nuevo Herald/Tampa Bay Times poll.

Mack narrowed the margin to 47 to 42 percent, three points tighter than it was last month, but the Fort Myers congressman didn’t seem to benefit from the eight-point surge of support for Republican Presidential candidate Mitt Romney in Florida.

Nelson continues to lead among voters who are not affiliated with any party, getting 51 percent support among independent voters to Mack’s 37 percent.

The Orlando Democrat also enjoys some crossover appeal, with 6 percent of the voters surveyed voting for both Romney and Nelson.

“This isn’t a wave election so you may see some purposeful ticket-splitting because people are a little bit divided in their view over what the parties are offering,’’ said Mason-Dixon pollster Brad Coker.

The telephone survey of 800 registered Florida voters — all likely to vote in the November election — was conducted Oct. 8-10 for the Tampa Bay Times, Miami Herald, El Nuevo Herald, Bay News 9 and Central Florida News 13. The poll, which included respondents using land-lines and cell phones, was conducted by Mason-Dixon, a nonpartisan, Jacksonville-based company. The margin of error is 3.5 percentage points.

Nelson’s lead may be steady but he’s not out of the woods, said Coker. “Anytime an incumbent is under 50 (percent) you sort of have to really watch the race,’’ he said.

The steady number of undecided voters “might give Mack a little bit of hope,’’ because more than half of them lean Republican, Coker said.

Among the undecided voters, 4 percent also said they are supporting Romney and 1 percent are supporting President Obama; two percent are undecided in both races.

“There is the potential there for Romney to pull Mack up,’’ Coker said. “My only question is, does Mack have the organization and campaign and resources to make it happen? He can’t just rely on coattails.”

The two candidates in the race who are running with no party affiliation — Chris Borgia, an Iraqi war veteran from Fort Lauderdale and Bill Gaylor a Marine Corps veteran from Indian Harbor Beach — drew 3 percent and one percent of the vote respectively.

That indicates voters still “don’t like Nelson, but they’re not comfortable with Mack,” Coker said.

The independent candidates could both serve as spoilers, Coker said, pulling enough votes from Mack to keep him down.

“Nelson could get 48 percent of the vote, but if these two independents suck off two percent, Mack can’t win,’’ he said.

Nelson has continued a steady barrage of negative attacks ads against Mack, while Mack has had the support of third-party organizations, including the conservative Americans for Prosperity and the political committee run by Sen. Rand Paul, which have run attack ads on his behalf against Nelson.

In the last month, Nelson has seen his favorability ratings rise from 33 to 39 percent while Mack’s have remained flat. Nelson continues to lead in Southeast and Central Florida, while Mack leads in North Florida and Southwest Florida, Mack’s home territory.