A new poll showing Democratic Sen. Bill Nelson with a large lead over Republican challenger Rep. Connie Mack IV — and showing President Barack Obama clinging to a razor-thin lead in Florida — has reawakened allegations from the Mack campaign that results are skewed.
At the same time, polls are showing varying results in the presidential race, with some reporting a major surge to a lead by Mitt Romney in Florida since last week's debate and others showing Obama holding a narrow lead despite movement by Romney.
At issue is the argument Republicans have made this year that published polls count too many Democrats, showing unrealistically high numbers for their candidates.
In the past, Democrats have made the same argument, saying polls that showed Republican candidates leading oversampled Republicans.
Most pollsters respond that they don't seek any specific partisan makeup in their samples. Instead, they seek a random sample that matches the age, gender and race of the general population, then ask the respondents what party they are.
This party "self-identification," they say, can vary with the political climate, resulting in a sample that doesn't appear to match the state's voter registration figures or the partisan breakdown of voters in past elections.
This week, questions have been raised about a poll released by the Marist College Institute for Public Opinion, done for NBC News and the Wall Street Journal.
It showed Nelson up by 13 points among likely voters — 52-39 percent, with a 3.1-point error margin — in what was expected to be a close race.
In the same poll, Obama led Mitt Romney by one point, 48-47 percent, well under the error margin.
At the same time, a poll by Mason-Dixon Polling & Research showed very different results: Nelson leads Mack, but by only five points, 47-42 percent, with a 3.5-point error margin.
It also showed Romney moving to a 51-44 percent lead over Obama, up from Romney's 47-48 deficit in the same poll last month.
Democrats blasted the Mason-Dixon poll, while Mack campaign manager Jeff Cohen called the Marist poll "utter nonsense."
Cohen said the Marist poll included 37 percent Democrats, 33 percent Republicans and 29 percent Independents — a mix with more Democrats and independents than are likely to show up in the November election, he said.
In 2004, he noted, the number of Republicans voting in Florida exceeded the number of Democrats, and minor party or no-party voters were only 21 percent of the electorate, not 29 percent.
The Marist pollsters replied that they don't "weight" their sample for any partisan breakdown, but they denied the sample they used was unrealistic.
They noted that 2004 was a Republican wave election, and that in 2008, more Democrats than Republicans went to the Florida polls.
And, they said, when they asked their respondents about voter registration — regardless of what party they most believed in — the results closely matched the actual state registration figures.
Other critics noted that the Marist poll included a high percentage of respondents who identified themselves as Hispanic, 20 percent, and that non-Cuban Hispanics tend to lean Democratic.
In 2008, only about 14 percent of Florida voters were Hispanic, according to CNN exit polls. But Marist pollster Lee Miringoff said his figure reflects Florida's increasing Latino population, and that the Hispanics included a larger-than-normal contingent of Cubans, who tend to lean Republican in Florida.
Pollster Brad Coker of Mason-Dixon said his poll was weighted so it would roughly match the actual partisan breakdown of voters in past Florida elections, while also maintaining a good demographic balance.
State Democratic Party Executive Director Scott Arceneaux said the Mason-Dixon poll "is malarkey."
"We always knew this race would come down to the wire, but we've crushed the Republicans in voter registration for eight straight months, built the largest strongest ground game this state has ever seen, and we're confident heading into the final stretch."
Democrats also noted that while they still trail Republicans in absentee ballot requests, they're much closer than in 2008.