Facing mounting pressure from tea party groups who accused him of acting unethically, one of the leaders of a campaign to pass a transit tax referendum in Pinellas announced on Wednesday that he is resigning.Ronnie Duncan, a former Pinellas commissioner and chairman of the Tampa Bay Area Regional Transportation Authority, said he's leaving his post as co-chair of the Yes for Greenlight campaign, which he helped launch earlier this month to support a referendum that would raise Pinellas' sales tax to pay for mass transit.Duncan said he has become an unwanted distraction, something the campaign can't afford in the runup to the November election. His resignation is the first major upheaval in a campaign that is still coming together.From the moment his involvement was announced, Duncan has been attacked by Pinellas and Hillsborough tea party groups, whose members accused him of interfering in a local ballot question on transit while simultaneously leading the area's state-funded transit agency. Even if his dual roles weren't technically illegal, they argued, they were unethical. Duncan responded to the criticism at first by quoting the advice of TBARTA's attorney, who argued that as long as Duncan made it clear he was acting as a private citizen, he could continue to lead Yes for Greenlight. But when the attacks continued, he decided to step down."I'm not doing this because I agree with them," he said. "I'm doing it because if we're not careful, it could cast a doubt on an otherwise very positive and aspirational campaign."Duncan, who was re-appointed to TBARTA's board by Gov. Rick Scott in 2013, said neither the governor nor his staff asked him to resign from the campaign. His decision means he will no longer be involved in planning the campaign's strategy, he said, and will not help with its fundraising.Duncan said he is being replaced by Don Ewing, president of a group called the Council of North County Neighborhoods, who like him is a North Pinellas resident and a vocal advocate for an expanded bus system and light rail. The campaign's other leader, Chris Steinocher, president of the St. Petersburg Chamber of Commerce, will continue to oversee its daily operations.In response to similar concerns over public perception, Yes for Greenlight has also severed ties with Tucker Hall, the Tampa-based public relations firm it brought on to manage nearly every aspect of the campaign. Tucker Hall was first hired over a year ago by Pinellas County's transit agency to design its more than $400,000 public education campaign for the transit referendum. Ultimately, the fact that the company had worked on the public campaign — which, by law, had to maintain a neutral position on the referendum — and was orchestrating the private advocacy campaign, worried Yes for Greenlight's leaders. It also fueled the referendum's opponents, who have complained for months that the public education component was little more than a poorly disguised advocacy campaign."There was no legal problem, but it was the same perception of conflict," Steinocher said. "Part of this was the notion of: Let's make sure that how we're running the campaign doesn't become the story."Steinocher said Tucker Hall will likely be replaced by several different consultants.Anna M. Phillips can be reached at [email protected] or (727) 893-8779.