If the campaign signs springing up around town are the most visible sign of the current election season, and the robo-calls and mailers its constant drumbeat, then the routine roll call of endorsements is the background noise.

While rarely revelatory, they are a signal to voters and thus a required part of any bid for public office, political experts say.

"It is incumbent that you have them," said David McCuan, a Sonoma State University political scientist. "Do they sway voters? No. But they point voters in a direction."

In announcing their latest endorsements last week, Susan Gorin and John Sawyer did some more pointing to voters.

The rival Santa Rosa City Council members are seeking the open 1st District seat representing Sonoma, Sonoma Valley and some of eastern Santa Rosa on the Sonoma County Board of Supervisors.

On Tuesday, Gorin rolled out an endorsement from Shirlee Zane, the Board of Supervisors chairwoman and the only continuing supervisor to endorse so far. (Supervisor Valerie Brown, the retiring 1st District incumbent, backed Sawyer last month.)

Zane called Gorin an ally in support of robust county health and human service programs, smart fiscal oversight and environmental protection.

"I think Susan is much better equipped in terms of her background, beliefs and decision-making," Zane said in an interview. "I think she'll be bold."

Gorin said Zane's support showed the backing her campaign has among county leaders and in the community. "I know I will work very well with her," she said of Zane.

Sawyer, meanwhile, rolled out endorsements Friday from a trio of current and former Sonoma council members, including Mayor Joanne Sanders.

Sanders made an unsuccessful bid for the 1st District seat in the June primary. She cited Sawyer's platform on economic development, pension changes and road repair as reasons for her support.

Sonoma Councilman Tom Rouse joined her in supporting Sawyer, as did former Sonoma mayor Doug McKesson, who had previously backed Mark Bramfitt in the primary.

Sawyer, who like Gorin is a Santa Rosa resident, said the endorsements reflected "a growing base of support in the Sonoma Valley."

By now, less than 40 days before the election and two weeks before mail-in voting begins, the list of high-profile backers for both sides — it is pages long for each — is likely almost complete, political observers said.

Among the names added this week, Zane's could carry the most sway in eastern Santa Rosa, where many of the critical 1st District voters live, McCuan said.

"Zane is on the board," McCuan said. "Her endorsement says that if Susan gets on the board there will be a strong working relationship."

Sanders' endorsement of Sawyer could pay off in a smaller pool of Sonoma voters, McCuan said. The three-term councilwoman is stepping down at the end of this year.

The larger list of endorsements in the two corners have few if any surprises, McCuan added.

Gorin has landed key endorsements from the county's largest labor group, SEIU Local 1021, as well as its largest environmental groups, nearly all of the county's elected state and federal officials and the Democratic Party.

Sawyer has support from the largest business and agriculture organizations, including the Sonoma County Alliance and Sonoma County Farm Bureau, Sheriff Steve Freitas, groups representing county law enforcement, and real estate and building associations.

The same battle lines developed in the last election for an open county seat, notably in the race to replace south county Supervisor Mike Kerns. David Rabbitt, supported by many of the same interests backing Sawyer, prevailed over Pam Torliatt, who had many of those now in Gorin's camp.

"Past battles will continue to color this race," McCuan said. That includes divisions between Gorin and Sawyer on the Santa Rosa City Council and standoffs between the opposing interests on the county board.

Key issues include the strength of land use regulations, county spending on roads, open space and economic development, and fiscal oversight, including looming board debates about possible tax increases.

In the coming weeks, voters will likely see the campaigns — and independent committees backing each — square off and go negative along those lines, observers predicted.

Several candidate events will ensure some of that tussle happens live. They include an Oct. 10 forum, sponsored by the Kenwood Press and the Valley of the Moon Alliance, at 6:30 p.m. at Kenwood School; and an Oct. 18 forum, sponsored by the League of Women Voters, at 7 p.m. at the Sonoma City Council community room, 177 W. First St.

In the meantime, any remaining endorsements rolled out by the campaigns may prove the only reprieve amid the onslaught of mud, McCuan said.

"Since so many people are voting by mail, it's happening earlier and earlier," he said.

(You can reach Staff Writer Brett Wilkison at 521-5295 or brett.wilkison@pressdemocrat.com.)