Republican Assemblywoman Catharine Baker has a bull’s-eye on her back.

As the Bay Area’s only Republican lawmaker — Assembly, state Senate or Congress — the Dublin attorney is the prime target for California Democrats looking to make her 2014 election a one-time aberration.

Baker, 45, is confident her bipartisan approach to legislating fits her suburban district, which stretches from Walnut Creek and Lafayette to Pleasanton and Livermore.

“I’ve got a different approach,” she said in an interview. “I’m willing to work outside party lines.”

But Democrat Cheryl Cook-Kallio, a 61-year-old former Pleasanton city councilwoman, argues that Baker’s record as a GOP legislator “speaks for itself.” The district’s residents want a lawmaker who will be aligned with them on important issues, she said, “someone who will stand up for education and woman’s health care.”

Cook-Kallio, who is retired from teaching government and U.S. history at Irvington High School in Fremont, says public service has always been important to her.

“I’ve taught thousands of kids to get active and involved in the community,” she said. “There are quality-of-life issues (in the district). ... I want to provide services.”

Contentious campaign

As a former teacher, Cook-Kallio said education issues are a priority. On Democrat-backed efforts to provide preschool for all California 4-year-olds, it’s a case of “pay now or pay later,” because children from low-income families who don’t attend preschool are instantly behind children who do.

Baker clings close to what she calls her record as a bipartisan problem solver, willing to work with Republicans or Democrats.

She stands with the Legislature’s Republicans in backing Gov. Jerry Brown’s call to put more money into paying down state debt and into California’s rainy-day fund to ease the pain of any future economic downturn.

“We know things are going to go south someday so we need to shore up state finances now,” Baker said. “We can’t spend money on long-term obligations.”

But she broke with many GOP leaders when she backed a tax increase on managed care health organizations, saying it was needed to qualify for more than $1 billion in federal money for health care for the state’s poor.

The contest already is shaping up as one of the state’s most contentious legislative races.

Only days after being sworn in as Assembly speaker, Anthony Rendon, D-Paramount (Los Angeles County), said that taking back Baker’s 16th District seat was the Democrat’s top priority and that the party would give Cook-Kallio “all the support she needs.”

Wide early lead in finances

That could be an expensive promise. When Baker beat Dublin Mayor Tim Sbranti two years ago, it was one of the most expensive legislative contests in the state, with outside groups pouring millions into the race.

By the time the final results were in, Baker and her backers had spent about $3 million, while the effort for Sbranti, a teacher and union official, had collected about $5.7 million.

Baker has a wide early lead in the money race, with $750,000 in the bank as of April 23, the cutoff date for the most recent state campaign finance report. Her donors include businesses such as Anheuser-Busch, 7-Eleven and Edison International, and political action committees for groups such as the California Apartment Association, Western Growers and the California Restaurant Association.

Her campaign also has collected checks from groups in the construction industry, including Associated General Contractors, Ponderosa Homes, the California Mortgage Bankers Association and the Northern California carpenters union.

Cook-Kallio has about $129,000 cash on hand, with much of her money coming from unions and Democratic officeholders. Already, 14 Assembly Democrats have given $4,200 each to her campaign while the California Nurses Association, the California Teachers Association, the Alameda Labor Council and a number of public employee unions also have chipped in.

With only two candidates in the race, both Baker and Cook-Kallio have guaranteed slots on the November ballot, but that doesn’t mean they’re taking the primary lightly. The June vote will provide a snapshot of where the district’s voters stand, letting each campaign — and their deep-pocketed supporters — see what needs to be done in the fall.

“I hope to do as well as possible in June,” Cook-Kallio said. “I’m pleased with the support I already have.”

Constituents more moderate

State party leaders, though, are already looking ahead to November, when they expect the anticipated Hillary Clinton and Donald Trump presidential matchup at the top of the ticket to bring Democrats out in droves.

Baker knows Democrats hold a 39 to 31 percent registration edge in her district, but argues that the voters are anything but the hard-core partisans found elsewhere in the East Bay.

“What happens in June is important,” she said. “I’m working my tail off. If I don’t do well, it will make my job harder in November.”

John Wildermuth is a San Francisco Chronicle staff writer. Email: jwildermuth@sfchronicle.com Twitter: @jfwildermuth