When Pete Stark walks into a room nowadays, his supporters get a bit nervous.

As he entered a Hayward union hall last Saturday, campaign volunteers greeted the 20-term congressman with warm applause and then fell quiet as he got ready to speak, flanked by other local candidates and a few cute kids.

What, everyone seemed to wonder, would the famously unpredictable and irascible 80-year-old say today?

"It's the kids and the grandkids that are really important in this effort," Stark said. "It's important for these guys so we have education and health care for them. ... That's what this is all about."

The line brought more applause and, no doubt, a collective internal sigh of relief. This time, there was no mention of challenger Eric Swalwell, no calling him a "pipsqueak" or baselessly accusing him of a felony, as Stark did in April. There was no flash of the congressman's legendary temper, no threat to politically crush those who cross him, as there was in August.

This was the Pete Stark many East Bay voters have known and loved for 40 years, but it was also the Pete Stark who's now mired in a campaign of contradictions.

He's in the political fight of his life -- against a fellow Democrat. He's in one of California's most fascinating House races, but one that means nothing to Congress' balance of power. Stark is running on his record, but is most to blame for elevating his insurgent challenger from distant long shot to serious contender.

For decades, no Republican could unseat this liberal lion in so heavily Democratic a district, and no primary challenger ever came close. But thanks to California's new "top two" primary system -- in which the top two vote-getters regardless of party go on to November's general election -- Stark now faces Swalwell, a Dublin councilman and Alameda County prosecutor.

The situation is poignantly familiar for Stark, an Air Force veteran and banker who first won office in 1972 by unseating an octogenarian, 14-term Democrat whom he cast as out of touch with a new electorate and modern times.

Swalwell, 31, correctly predicted that both the top-two primary and a radical redrawing of Stark's district, now including Dublin and other nearby communities, could boost his bid. And Swalwell correctly foresaw that Stark's well-known thin skin and sharp tongue might do some of his work for him.

But even after months of relentlessly baiting Stark by painting him as an out-of-touch politician who lives mostly in Maryland and has missed too many House votes, Swalwell still looked stunned at a candidates' forum last April in Hayward, where Stark accused him of taking "hundreds of thousands of dollars in bribes" for Dublin land-use votes.

It wasn't true, and it took Stark more than a week to admit as much; even then, he made other accusations against Swalwell that he was later forced to retract. In the following weeks, he would goof up his facts during meetings with newspaper editorial boards.

MSNBC eventually picked up Swalwell's attack line that Stark has issued "more public apologies than Lindsay Lohan."

This is the kind of campaign other Democrats chose not to wage, or dared not. State Sen. Ellen Corbett, D-San Leandro, for example, wants Stark's seat in Congress but wouldn't take him on. Ditto for Ro Khanna, a former Obama administration official who raised a jaw-dropping $1.2 million in 2011's last quarter with help from national Democratic benefactors, yet won't run until 2014, when it's widely expected Stark will retire if he's not defeated this year.

Yet nationally, "nobody cares," said Gary Jacobson, a UC San Diego expert in congressional elections, because most attention is fixed on who will control the House next year, and this will remain a Democratic seat no matter what.

With candidates of similar ideology, he said, voters base decisions on name recognition and personality. Stark has the name recognition, but perhaps not the more endearing personality. "These are the kinds of conditions under which some of the old guys get knocked off," Jacobson said.

Stark -- who finished six percentage points ahead of Swalwell in the June primary, while a conservative independent candidate failed to make the cut -- contends that Swalwell, with less than two years of experience in elected local office under his belt, is an over-ambitious novice who lacks the know-how to grapple with the next Congress' big issues, from budget cuts to implementation of Obamacare. Yet Stark since the primary has refused to meet Swalwell for more debates. He posts Web videos and sometimes shows up to rally campaign volunteers, but mostly he's lying low and letting his incumbency -- and a reservoir of affection he's built up among local liberals -- do the heavy lifting.

Stark told a reporter Saturday that it's gratifying to see second and even third generations of local voters coming out to support him. He's worked hard for the district, he said, and "it's been good to me."

But Swalwell on Wednesday said all those voters "count on their representative to speak for them in Washington and to them at home. But Congressman Stark is in hiding, and all we hear is the sound of silence."

On the campaign trail, Swalwell has kept calling attention, however obliquely, to Stark's age, either by jabbing at the Social Security benefits that Stark's kids collect or by going out of his way to make himself look as young and vital as possible -- training with county firefighters, sparring with a police dog and so on -- as if to say, "Look what I can do and Pete Stark can't."

He's also been knocking on doors all over the newly drawn 15th Congressional District in search of voters like Elisabeth Olander, 54, an independent-minded Democrat who's married to a Republican and was eager to chat with the candidate on her doorstep one evening early last month.

"I believe if you want the job, you should go door to door and tell us why," she said. "I respect you for doing that."

Stark, who started using a cane in recent years, relies on longtime supporters like those at the union hall last weekend.

They included Oakland resident Susan Hammer, 65, who lives outside the district but said she's glad to walk precincts for him. "He's always been vocal in terms of working families, working class people," she said. "That's why I'm a Pete Stark fan: He's kept his focus. He hasn't strayed from the path."

This year, however, the path is bumpier. Abel Maldonado, who as a state senator in 2009 masterminded the top-two primary, says the new system means Stark "cannot kick back and relax. He's got to campaign, he's got to keep talking to the people in that district ... and that's good for that area."

Josh Richman covers politics. Contact him at 510-208-6428. Follow him at Twitter.com/josh_richman. Read the Political Blotter at IBAbuzz.com/politics.

Stark's campaign gaffes
April 10: At a candidates' forum in Hayward, Stark says Swalwell accepted "hundreds of thousands of dollars in bribes" from Dublin-area developers -- and that Swalwell has a spotty voting record.
April 18: Stark issues a statement apologizing for having "misspoke" in making the April 10 allegations, but voices "concerns about my opponent's behavior" including Swalwell's votes for projects "by developers who have been raided by the FBI" and "have plead [sic] guilty to destroying natural habitats."
May 1: At a San Francisco Chronicle editorial board meeting, Stark accuses a columnist of having contributed to Swalwell's campaign. Pressed for evidence, he flips through a folder he said was compiled by his 16-year-old son, finds nothing to back his claim, and apologizes. In the same meeting, he confuses defunct Fremont solar manufacturer Solyndra with electric-car manufacturer Tesla.
May 3: At a Bay Area News Group editorial board meeting, Stark acknowledges he lacked evidence to back his April 18 claims: "I'll concede to that, apologize for it, and let's get back to issues."
July 3: At a Union City event, Stark gets angry as reporters ask whether his age is an issue in this race. Asked why he won't debate Swalwell, he replies, because "we'd only get stupid questions like you're asking that have nothing to do with issues."
Aug. 8: Former Assembly Majority Leader Alberto Torrico, D-Newark, tells the Chronicle that when he called Stark to say he would be endorsing Swalwell, Stark responded by yelling at him, questioning his sanity and vowing that if Torrico ever ran for office again, "I will squash you."

Democrat VS. Democrat
Fortney "Pete" Stark Jr.
Party: Democrat
Age: 80
Hometown: Fremont
Education: Bachelor's in general engineering, Massachusetts Institute of Technology (1953); master's of business administration, UC Berkeley (1960)
Experience: Congressman since 1973; earlier, founded Security National Bank in Walnut Creek (1963)
Online: www.petestark.com

Eric Swalwell
Party: Democrat
Age: 31
Hometown: Dublin
Education: Bachelor's in government and politics, University of Maryland (2003); law degree, University of Maryland School of Law (2006)
Experience: Dublin councilman since 2010; Alameda County deputy district attorney since 2006
Online: www.swalwellforcongress.com

Stark, swalwell: The issues
Rep. Pete Stark: Even after 40 years in the House of Representatives, the incumbent says he still has more to do, such as protecting Medicare and Social Security for future generations; cutting military spending; advancing education bills for disadvantaged children; and bringing home more federal funding for local infrastructure projects. He's proud of having authored the COBRA health-insurance continuation law; helping to craft the Affordable Care Act; and securing aid for workers laid off from the NUMMI auto plant.
Eric Swalwell: The challenger notes how Dublin successfully controlled costs in recent years, including a deal with workers on pension contributions. He wants to see such fiscal discipline in Washington, where the national debt threatens national security. And he talks about leveraging research at Lawrence Livermore Laboratory and elsewhere to create a "Green Valley" where the clean technology industry can take root.
Both of the contenders would raise the Social Security payroll tax cap and scale up the retirement age. Swalwell would repeal the "No Child Left Behind" education law, which he says labels schools as failures without giving them tools for success and handcuffs teachers with excessive testing; Stark would amend the law so teachers are evaluated and rewarded for good work with less emphasis on teaching to tests. And both call for a speedier-than-planned withdrawal from Afghanistan and continued sanctions and diplomatic pressure -- not military force -- to keep Iran from developing nuclear weapons.