For nearly 30 years, not a single Republican incumbent on the Pinellas County Commission has lost a general election. Voters ended that legacy Tuesday, ousting two commissioners among the board’s more conservative voices.

In the end, the races did not turn out to be the nail-biters that some had predicted. Republican Commissioner Neil Brickfield lost his District 1 seat to Democratic challenger Janet Long by almost 11 percentage points, prompting him to concede the race before 8 p.m. Commissioner Nancy Bostock, a Republican from Treasure Island, lost her District 3 seat by a slimmer margin — about 5 points — to former state Sen. Charlie Justice, a Democrat from St. Petersburg.

At a tense Republican watch party at the Hilton St. Petersburg Carillon Park hotel Tuesday night, Brickfield and Bostock blamed their losses on one issue: fluoride.

The pair were part of a bloc of commissioners who voted a year ago to stop adding the cavity-fighting mineral to the county’s drinking water.

The four commissioners who opposed fluoride said they were motivated by concern for public health while critics called the vote as a capitulation to tea party extremists who believe fluoride is harmful.

“The voters clearly said they want fluoride in the water,” Brickfield said. “And I will never vote against fluoride again as long as I live.”

Bostock said the fluoride issue was unfairly emphasized by the Tampa Bay Times in its election reporting and editorials. Throughout their campaigns, both candidates stuck by their votes and denied that fluoride was a major topic on voters’ minds.

“When I was out in the community the topic of fluoride came up very, very little. But the coverage of it was excessive,” Bostock said.

Their historic losses were part of what appeared to be a strong showing for Democrats across Pinellas County. On Tuesday night, with all 299 precincts reporting but 9,500 absentee ballots yet to be counted, unofficial results had the Democrats with two new seats on the County Commission and two more in the Florida State House.

St. Petersburg Democrat Ken Welch, 47, easily won re-election to the commission, capturing 69 percent of the vote to 31 percent for political novice William “Buck” Walz, 33. Walz is a company operations manager from St. Petersburg who said he supported the county’s decision last year to stop adding fluoride to county drinking water.

Long and Justice both attributed their success to fluoride, an issue they seized on early in the election and used to convince voters that the Republican commissioners were reactionary and deaf to dentists’ appeals. Long ordered molar-shaped decals with the words “Pro Fluoride!” printed on them and stuck them on her larger campaign signs.

On Tuesday night, Long drank champagne and celebrated her election and her 68th birthday while wearing an orange T-shirt Justice had ordered. The back said: “2012: Time to rinse & spit.”

“I attribute the win to fluoride, but also to the way the fluoride vote happened,” Long said Tuesday night. “If you’ve got people who are going to ignore science and empirical facts, then you have to wonder what other decisions they’re going to apply that to.”

“This is a huge win,” said Johnny Johnson, a Palm Harbor dentist who urged his colleagues to get behind Justice and Long. “Between the fluoride issue and the Tampa Bay Times holding the commissioners’ feet to the fire, they’ve really paid the price.”

Long’s campaign appeared to be in danger in September after she criticized fire unions on the eve of the anniversary of the Sept. 11 attacks. In a meeting with the Tampa Bay Times’ editorial board, Long said that firefighters “have really taken advantage of 9/11,” using the national tragedy for their benefit. Typically an organized and politically active group, firefighters immediately responded, creating a Facebook group in opposition to her election and vowing to rally around Brickfield.

Justice, who waited until after 9 p.m. for Bostock to concede, said adding fluoride back into the county’s water would be his first act as commissioner.

The long-running theme of Republicans holding on to commission seats ended only because of Brickfield and Bostock’s far-right positions, he said.

“Pinellas has a history of moderate Republicans,” he said. “But the two that were there were so out of lockstep with the people of Pinellas that we had to step up and take Pinellas back from the extremism.”

Bostock and Brickfield both won their races in 2008 with about 52 percent of the vote, a margin they considered an achievement in a year when Pinellas went for President Barack Obama.

In the four years that followed, the two commissioners became known as some of the most conservative members of the seven-person board, which for decades has been dominated by moderate Republicans.