SAN FRANCISCO — On the eve of today’s crucial Super Tuesday showdown in the presidential race, Senator Clinton’s campaign paid for an hour-long nationally televised town hall meeting designed to showcase what aides believe is her forte: tackling a wide range of policy issues in depth and detail.

The questions, which were selected in advance, spanned subjects such as immigration, education, and America’s reputation in the world. The only area where she alluded to a difference with her rival for the Democratic nomination, Senator Obama, was on health care.

“I’m the only candidate left in this race on either side who is committed to universal health care. It is not just an issue for me,” Mrs. Clinton said during the session, which was carried on the Hallmark cable channel. “I have been working on this for so many years.”

Asked about Iran, Mrs. Clinton stressed her position favoring talks with Tehran, though she did so in the context of a possible use of force against that regime.

“I believe we should be opening negotiations with Iran. I have advocated that for years,” she said. “There’s a lot of misunderstanding and hostility. I want the rest of the world to see that we are willing to do this. … If we do have to take action against them because of what they are doing to us or our allies, we have to exhaust every possibility.”

The Iran issue is one where Mr. Obama has gained the upper hand with some Democratic voters, in part because of attention to his statement that in his first year as president he would meet directly with the president of Iran, as well as the leaders of other rogue states like North Korea.

Last night’s telecast included several humanizing moments for Mrs. Clinton, including appearances by her family members. President Clinton, who spent the day barnstorming across California, wound up in San Francisco introducing a Vietnam veteran on the telecast to ask a question about injured veterans. The Clintons’ daughter, Chelsea, joined from Hartford, Conn.

When the cameras were turned on in her hometown, Park Ridge, Ill., Mrs. Clinton smiled broadly. “I could tell you stories about every person … but I won’t,” she said.

In San Francisco, Mrs. Clinton’s answer to a question about recognizing gay relationships drew a rousing cheer.

“I believe it’s important that we leave these decisions to the states,” she said. The former first lady noted her support for domestic partner benefits for federal workers and her opposition to the military’s Don’t Ask, Don’t Tell policy, though she neglected to mention her basic opposition to gay marriage.

Mr. Clinton listened intently to the televised meeting, even though he was up near dawn for an early campaign rally at a community college in Orange County, Calif. It was there that he took his most direct swipe of the day at Mr. Obama.

“You will either vote for a candidate who will provide quality, affordable health care for all Americans or one who thinks it’s not that important,” the former president told several hundred students and union workers, many of them Latino.

While not naming Mr. Obama, Mr. Clinton offered gentle contrasts by saying his wife would “deliver” and would be “a president who can execute good ideas.”

At noontime he was in Sacramento and in the afternoon he was in Stockton, Calif., where several thousand people attended a hastily arranged rally at the University of the Pacific. He honed in on the subprime mortgage crisis, which is severe in many of California’s smaller cities.

Mr. Clinton said his wife’s plan to keep people in their homes is “much more aggressive than any of the other candidates” and would stave off what he warned would be a “calamitous collapse” of the housing market.

“She is a world class genius at making positive change in other people’s lives,” he declared. There were also a couple of elbows for Mr. Obama, such as a passing reference to an alternative health plan that would “leave 20 million people out and waste a lot of money that we shouldn’t waste.”

On a day when Mrs. Clinton may have teared up again on the campaign trail, Mr. Clinton spoke of her emotions decade ago when she studied child abuse at the Yale Hospital in New Haven, Conn.

“She would come in in tears there, crying about kids being brought in the hospital with cigarette burns on their arms. Kids who had not been fed for 10 days or two weeks,” the former president said. He said the scenes motivated his wife to work on proposals for greater legal protections for children.