The candidates -- vying Nov. 3 for the seat left open when Rep. Ellen Tauscher resigned in June to take a U.S. State Department post as undersecretary for arms control and international security -- spoke before almost 300 people in a Saint Mary's College auditorium.

Although the seat has been in Democratic hands since 1996, Republican candidate David Harmer brought the largest and most vocal supporters Monday night.

He was joined by Democratic Lt. Gov. John Garamendi, who most consider the front-runner in the largely blue district, along with Green Party candidate Jeremy Cloward, American Independent Party candidate Jerry Denham and Peace and Freedom Party candidate Mary McIlroy.

With a house bill now including a public option to health care, the candidates shared their thoughts on the hot-button topic.

"The public option will act as a way in which to control the enthusiasm of private insurance companies when they try and rip us off," said Garamendi, a 64-year-old political veteran from Walnut Grove.

His Republican opponent called it "one mammoth monopoly government policy."

Harmer, a 47-year-old lawyer from San Ramon, offered four alternatives: allow customers to shop for insurance across state lines, remove tax penalties for people buying health care on their own, tort reform and association

When asked what advice they would give President Barack Obama on Afghanistan, Harmer echoed former Vice President Dick Cheney's words.

Harmer said Obama needs to stop "equivocating" and define the mission, provide resources to further that mission and stick with it.

Garamendi said military operations need to wind down and social and economic development plans need to ramp up. "We will not win this war militarily," he said. Once the education system is improved, the country will change itself, he said.

Harmer said if troops were withdrawn now it would create a "humanitarian catastrophe."

"I'm astonished that self-proclaimed liberals don't see the vacuum that would ensue," he said.

The two candidates shared similar views on a state water proposal that could include a peripheral canal.

Garamendi opposed the peripheral canal, saying that state should instead: pursue water conservation, urge Southern California to reuse its water, protect the Delta, shore up levies and improve storage.

Harmer says he's "highly skeptical" of a peripheral canal for the cost alone, but also potential water property rights violations as well. He said he would fight for local drinking, agricultural and environmental water concerns, and lastly the concerns of Southern California water stakeholders.

Cloward, a 38-year-old political science professor at Diablo Valley College who lives in Pleasant Hill, repeated throughout his remarks that military spending must be cut to properly fund other more important programs, such as education.

Denham, a 74-year-old insurance agent and financial planner from Walnut Creek, steered most questions back to the Constitution. The American Independent candidate vowed, if elected, to cut each federal agency by 25 percent and reduce the size of federal government by 90 percent.

McIlroy, 50, of El Cerrito, called for the immediate withdrawal of troops from Iraq and Afghanistan and proposed taxing oil and altering Prop. 13.

Monday's forum was sponsored by the Times and the League of Women Voters of Diablo Valley. Times political columnist Lisa Vorderbrueggen moderated the 90-minute debate.