FREMONT -- In their only matchup before the June 3 primary election, U.S. Rep.Mike Honda on Saturday night said he would continue to be a voice for the powerless in his Silicon Valley district, while former Obama administration official Ro Khanna said the region needs a new, more tech-minded representative.

The two Democrats, locked in one of the most closely watched congressional races in the United States, met at a packed candidates' forum at Fremont City Hall attended by more than 300 people, many of them waving signs and chanting before and after the event.

The biggest news of the evening, however, may have come afterward when Honda, in response to a question from this newspaper, agreed to debate Khanna in the future. For months the congressman, seeking an eighth term in a district that runs from Fremont to San Jose to Sunnyvale, has turned down multiple invitations to debate. Khanna has blasted Honda for agreeing to participate only in scripted events.

Honda promised that after the primary, in which only the top two candidates will advance to the November election, he will go head-to-head with Khanna on a debate stage.

"I think that makes sense because it will be one-on-one," said Honda, D-San Jose.

Khanna beamed when he heard the news.

"Great!" he said. "I look forward to them. I've always said the debates aren't about me or Congressman Honda. This is about the 17th District. This is the most unique district in the world, and I would love to have five or six substantive conversations on the economy, on the environment, on education and let's really excite the district and have a debate that elevates the dialogue."

Saturday's event, sponsored by the League of Women Voters, was billed as a forum, not a debate, because the rules prevented the candidates from asking each other questions.

The two men largely agreed on nearly every issue. Both said they support the right of women to have an abortion. Both said they oppose the Supreme Court decision to overturn parts of the Voting Rights Act. Both said they support immigration reform that will allow a path to citizenship for most people who are in the country illegally.

Honda, who was interned as a child during World War II because of his Japanese ancestry, emphasized his work to secure $900 million in federal funding to bring BART from Fremont to San Jose, along with his familiarity with Washington leaders, noting that he just met Friday with President Barack Obama to discuss the immigration reform bill.

"From my earliest memories in an internment camp to the two years I spent in the Peace Corps in El Salvador, I have not lost faith in our government," Honda said. "I am continuously trying to provide a voice for those people who don't have a voice."

Khanna said the federal government needs to do more to prepare young people for the 21st century economy. He urged that the government spend more on education, that computer coding be taught in public schools and that programs to bring women into engineering and science jobs be expanded.

"There are a lot of good people in Washington," he said, "but the system is broken and we need new ideas and new energy to move this nation forward."

Also on the stage was Republican Joel Vanlandingham, 47, a San Jose industry recruiter. Another Republican candidate, Dr. Vanila Singh, a Stanford anesthesiologist, did not participate.

Vanlandingham agreed with the two Democrats on a number of key issues, including calling for a carbon tax to reduce global warming emissions, and reducing military spending. Describing himself as "a man of faith," Vanlandingham said he opposes abortion, noting that he and members of his church hand out food to the homeless.

"If you are going to send me a check, send it to a charity. I don't want your money," he said. "I want you to sit down and evaluate the candidates and see who is going to represent you the best."

Under California's new open primary system, candidates from all parties appear on the same ballot. Even if one candidate wins more than 50 percent of the vote in primary, the two candidates who receive the most votes on June 3 will face off in the November election, regardless of their party affiliation.

But it's quite possible, given the Democrats' dominance in the district, that both Honda and Khanna could end up on the November ballot.

Registered Democrats outnumber Republicans 44 percent to 19 percent. Of note, however, a significant number of its voters -- 32 percent -- are registered with no party preference, the most of any of California's 53 congressional districts.

Honda, 72, is a former schoolteacher and principal. He served as a San Jose school board member, a Santa Clara County supervisor and state assemblyman before beating Republican Jim Cunneen in his first race for Congress in 2000. In every re-election race since, he has won by landslide margins of 30 percentage points or more. In Congress he has focused on civil rights, education and immigration issues, with votes that have consistently ranked him among the most liberal members of the House of Representatives. He is endorsed by President Obama, U.S. Sens. Dianne Feinstein and Barbara Boxer and a long list of labor organizations.

But this year Honda faces the race of his life. He has raised $1.91 million during the campaign, barely half of the $3.73 million that Khanna has raised.

Khanna, 37, is a former deputy assistant secretary in Obama's Commerce Department. He now works as an intellectual property attorney at Wilson Sonsini representing high-tech firms. He has been endorsed by Lt. Gov. Gavin Newsom and a long list of tech executives, including Eric Schmidt of Google, Sheryl Sandberg of Facebook, Marc Benioff of Salesforce.com and venture capitalist John Doerr.

Typically, political challengers seek to have as many debates as possible in campaigns as a way to raise their visibility. Incumbents -- particularly those whose internal polls show them with a lead -- try to avoid debates, which can spark verbal miscues or visual images that can harm their campaigns.

In 1976, President Gerald Ford's campaign took a hit when he incorrectly insisted in a debate with Democratic challenger Jimmy Carter that Poland was not dominated by the Soviet Union. Similarly, President George H.W. Bush faltered in 1992 when he repeatedly glanced nervously at his watch in a debate with Democrat Bill Clinton.

Sometimes incumbents can use solid debate performances to knock out their opponents, however, such as in 1984 when President Ronald Reagan, then 73, was asked about age and said: "I am not going to exploit, for political purposes, my opponent's youth and inexperience." The audience roared with laughter as Democratic challenger Walter Mondale watched his chances of victory evaporate.

"Ro Khanna is trying to offset a quarter-century of name recognition, and the best way he can do it is if he's face-to-face with his opponent," said Larry Gerston, a San Jose State political science professor, while Honda is "guarding what he believes to be a very good reputation and not exposing that to direct confrontation."

Joe Tuman, a San Francisco State professor and political communications expert, said incumbents often balk at doing many or any debates because they already have the name recognition and bully pulpit of elected office.

"If you're enjoying that advantage, why would you want to get up on a stage with challengers and basically lend some gravitas to their campaigns by your presence?" asked Tuman, now running his own Oakland mayoral campaign. "But whether incumbents like it or not, debates are now a regular tradition of every political race in this country. It's very difficult in this environment ... to have a good reason to avoid them."

Incumbents who have refused to debate include Sen. Feinstein, an entrenched Democrat who wouldn't face her shoestring-financed Republican challenger, Elizabeth Emken, in 2012. Although she was criticized for it, Feinstein won that race with 62.5 percent of the vote.

Some challengers take their debate demands to extremes: In 2010, Democrat Ray Lutz and Libertarian Mike Benoit went on an 11-day hunger strike to compel Rep. Duncan Hunter, R-El Cajon, to debate them. Hunter finally did, and he won the election with 63 percent of the vote.

Contact Paul Rogers at 408-920-5045. Follow him at Twitter.com/PaulRogersSJMN. Contact Josh Richman him at 510-208-6428. Follow him at Twitter.com/josh_richman. Read the Political Blotter at IBAbuzz.com/politics