Shirlee Zane will have a challenger after all in her bid for re-election to the Sonoma County Board of Supervisors.

Former Rohnert Park Councilman Tim Smith launched a bid Wednesday to unseat Zane in the June election, which means that all three supervisorial seats up for grabs will have contested races.

Smith, 57, ran unsuccessfully for the 3rd District supervisor's seat in 2008, placing third in a June primary, behind former Santa Rosa Councilwoman Sharon Wright and Zane, who went on to claim the seat in November.

An attorney specializing in business and estate planning, Smith served a single four-year term on the Rohnert Park council, including a year as mayor. He was ousted in the November 2008 election, when control of the council shifted to a business-oriented majority.

The 3rd District seat, which represents most of central Santa Rosa and Rohnert Park, was held for 20 years by Supervisor Tim Smith, no relation to the former Rohnert Park councilman.

Up until now, Zane, a former Council on Aging chief executive officer and the current board chairwoman, had been unopposed in her re-election bid.

Smith said he was jumping into the race partly to make sure the seat didn't go uncontested.

"The chance of serving and having an improved supervisor in the seat if nobody runs against the incumbent is nil," he said. "I think democracy deserves debate."

Smith on Wednesday pulled nominating papers and paid a $1,340 filing fee to enter the race, which has a filing deadline of March 9.

He also discontinued a blog, California Commons, that he has written on The Press Democrat's website since 2009.

Smith's campaign faces a "heavy lift," said David McCuan, a Sonoma State University political scientist.

Zane, 52, is a powerful incumbent with strong ties to some of the same environmental and union support that Smith might court, McCuan said.

"He's going to need not only money and some organization but folks out on the ground who are going to help him with that heavy lift," McCuan said.

Zane reported nearly $50,000 in campaign cash last month. Smith said he would seek to chip away at that edge, starting with a $3,000 personal loan to his campaign.

Smith said he had not yet prepared his campaign platform. "I might be what some people perceive as to the left of (Zane) environmentally and to the right of her on fiscal issues," he said.

He mentioned reducing the county's rising retirement costs, a campaign Zane has sought to lead. Smith said so far that effort has not produced any results.

"Sonoma County pensions have yet to be addressed," he said.

Zane countered, saying a report she crafted with Supervisor David Rabbitt will guide pension system changes through contract talks and legislative moves in Sacramento.

"It's more than a report. It's a strategic plan with very aggressive goals," she said.

She welcomed Smith's challenge, but at the same time lamented it as a "diversion."

"I'd rather give 110 percent attention to my job," Zane said.

During his tenure on the City Council, Smith and his allies, including current Mayor Jake Mackenzie, clashed with the Rohnert Park Public Safety Officers' Association and then-city manager Carl Leivo over employee benefits.

Smith opposed increased benefits and pushed to have them reduced. His 2008 ouster came after a strong campaign from the peace officers' association targeting him and other incumbents.

Smith said the fight would not limit his county campaign.

"I've had labor endorsements and I'm going to actively seek endorsements," he said.

But many of those endorsements have already been handed out. Mackenzie, the Rohnert Park mayor, for example, has already endorsed Zane.

He called Smith "a close friend" but said he was puzzled over his decision to run, calling it "quixotic."

The county's largest environmental group, Sonoma County Conservation Action, endorsed Zane this week.

The leading labor coalition, the North Bay Labor Council, endorsed Zane in 2008. It has not issued endorsements for this election cycle, but its leader said Smith would have to fight hard to wrest its support away from Zane.

"She is a zealous advocate for her constituents," said Lisa Maldonado, the council's executive director. "Not just Tim Smith, but any candidate would have to work hard to convince labor that they should change their endorsement."