With 53 Members of Congress — more than any state has ever had — California wields enormous political clout. But thanks to air-tight House district boundaries that strongly favor one party or the other, the battle to control the House this fall will largely bypass the Golden State — again.

However, California is home to a few districts that hold interest for politicos because of the longer-term demographic changes taking place within their borders. While it would take a massive partisan tide this fall to shake loose the incumbents who currently hold these districts, the demographic churn now under way could make these seats hotly contested later this decade.

“You never know what’s going to happen,” said Sal Russo, a Sacramento-based Republican consultant.

State lawmakers’ desire to draw a status-quo map after the 2000 Census made intraparty demographic fights inescapable. Minority groups were outraged when three majority-minority districts in the Los Angeles area were tailored to elect white incumbent Reps. Brad Sherman (D), Howard Berman (D) and Adam Schiff (D).

And Asian-American groups’ hopes for a majority-Asian district in the San Francisco Bay area were dashed, at least for the moment.

For now, the closest thing to a competitive California race this year is the open-seat fight in the 20th district, which runs from Bakersfield to Fresno in the Central Valley.

The 20th district is witnessing two volatile demographic trends. The region’s agriculture makes it a magnet for migrant labor, so the district is potentially fertile territory for liberal groups seeking to elect a Democrat — if they can energize Hispanics and other farm workers who are eligible to vote.

At the same time, suburbanization is pushing outward from Fresno and Bakersfield. This has made large swaths of the valley more conservative — good news for Republicans.

This year, two veteran lawmakers, former state Sen. Jim Costa (D) and current state Sen. Roy Ashburn (R) are vying to succeed retiring seven-term Rep. Cal Dooley (D).

Most signs point to a comfortable Costa victory. Half of the district’s registered voters are Democrats, and Costa represented most of the area contained within the 20th during his 24 years in the Legislature. Despite a stiff primary fight with former Dooley Chief of Staff Lisa Quigley, Costa captured an eye-popping 71 percent of the primary vote.

Some Republicans, however, hope that Quigley’s attacks on Costa’s voting record and personal troubles — he was arrested in the 1980s for soliciting a prostitute, and police found drug paraphernalia in his home in 1994 — softened him up for the general election. Ashburn is a well-known and well-respected figure in the valley, and the district is, despite its Democratic leanings, relatively conservative.

“He’s doing very well, and especially in light of what happened in the [Democratic] primary, this race has moved up on our radar screen,” said Carl Forti, communications director for the National Republican Congressional Committee.

Forti said Costa “has a lot more history that needs to be explored.”

Ashburn, who spent 12 years on the Kern County Board of Supervisors and six years in the state Assembly before being elected to the California Senate in 2002, said he does not expect Costa’s personal life to become a factor in the general election. Rather, Ashburn plans to highlight the differences between his voting record and Costa’s.

“He voted to create a hostile environment for business and economic development,” Ashburn said.

Despite that line of attack, even some Republicans concede that Costa is a difficult target for Ashburn.

“They’re both problem-solving legislators and neither is in to grandstanding,” said Russo, who worked for Ashburn’s legislative campaigns but has not signed on to his Congressional bid.

Despite Democratic confidence, Costa will need to rebuild his war chest after spending more than $800,000 on his hard-fought primary win. As of March 31, he had just $23,000 in the bank, compared to $139,000 for Ashburn.

But with the NRCC expected to have more money at its disposal this cycle than the Democratic Congressional Campaign Committee will, national Republicans may choose to pour some money into the 20th district just to play somewhere in the most populous state in the country.

“I like being the only race in California,” Ashburn said. “California’s its own nation. It may not be great for good government, but it’s great for the race.”

And Ashburn, who does not have to sacrifice his Senate seat to run this year, has little to lose by running this time — and could have a leg up if a new House district is created in the Central Valley in the next few years.

Another district being buffeted by demographic change is the 45th district, which runs east from the necklace of retirement and tourist havens — Palm Springs, Palm Desert and La Quinta — through scattered desert settlements until it ends at the Nevada border. Though in recent decades this region has been increasingly affluent, the eastward-barreling Los Angeles metro area has brought a growing number of immigrants and working-class residents.

In the 45th, Democratic real estate investment manager Richard Meyer will take on four-term Rep. Mary Bono (R) in November. Meyer — who defeated a car valet in the March 2 Democratic primary — is considered the longest of long shots against Bono, the widow of vocalist and former Rep. Sonny Bono and a high-profile figure in her own right.

The area’s changing demographics undergird what is already a rather marginal district. The 45th would have given Bush 50 percent of the vote had it been structured in 2000 like it is now. Democrats believe they’ll be competitive there once Bono moves on — which they hope will be sooner rather than later.

Meanwhile, Republicans dream of ousting Rep. Loretta Sanchez (D) in the ethnically diverse 47th district, based in Orange County.

This fall’s Republican nominee, Orange County Board of Education Member Alexandria Coronado, notes that despite a 14-point Democratic edge in voter enrollment, a full 62 percent of the district’s residents voted to recall then-Gov. Gray Davis (D) last October. What’s more, in the race to replace Davis, Democratic Lt. Gov. Cruz Bustamante took just 37 percent of the vote. The two principal Republican candidates, now-Gov. Arnold Schwarzenegger and state Sen. Tom McClintock together pulled in 63 percent.

But while Southern California GOP officials — including a few Republican Members of Congress — lobbied Coronado to challenge Sanchez instead of running for a reliably Republican seat in the state Assembly, Coronado — a single mother — remains a long shot, lagging badly behind Sanchez in fundraising. Through March 31, Coronado had just $20,000 in her campaign account; Sanchez, a financial powerhouse since upsetting then-Rep. Bob Dornan (R) in 1996, had $1.4 million.

The race to succeed retiring Rep. Doug Ose (R), a leading House moderate, is also attracting some attention this year.

In a Sacramento-area seat once held by longtime Democratic Rep. Vic Fazio, successive redistrictings favorable to the GOP have created a district in which Republicans represent 45 percent of enrolled voters, compared to 36 percent for the Democrats.

This means that former state Attorney General Dan Lungren (R) — a staunch conservative who survived a bitter primary — remains the heavy favorite in November. Lungren took just 38.5 percent of the vote in the three-way primary in March, and Democrats hope that fissures remain from the primary.

“Lungren, in his rush to the right with [state Sen. and primary runner-up Rico] Oller, may have put himself out of step with his district,” said Greg Speed, a spokesman for the Democratic Congressional Campaign Committee.

But while the Democratic nominee, financial adviser Gabe Castillo, has emphasized his credentials as a moderate, he is likely to be badly underfunded.