The millions spent, the nasty ads and the big-name outside help are a testament to the tight, high-stakes California special election to replace Republican Randy "Duke" Cunningham, the disgraced former lawmaker doing time for accepting millions in bribes.

The winner of the June 6 contest will serve the seven months remaining in Cunningham's term and get a decisive boost for the November election. No wonder the parties are throwing everything at the race.

More than $10 million has been spent on television ads, phone banks and mailings. Vice President Dick Cheney plans to headline a $2,100-per-person luncheon Tuesday for Republican Brian Bilbray, the former congressman looking to return to the House.

In any other election year, Bilbray would likely coast to a win in the heavily GOP district. But ongoing investigations of political scandals, President Bush's falling approval ratings and discontent with the GOP-led Congress has left Bilbray in a close race with Democrat Francine Busby, a local school board member.

Republicans are eager to avoid an embarrassing loss — or even a squeaker — in one of the last electoral contests before November. Democrats hope an upset win gives them the momentum to reclaim the majority in the House in the midterm elections. They need 15 seats to take charge.

"This is a canary-in-the-coal-mine election," said Jack Pitney, a political scientist at Claremont McKenna College. "If Bilbray ends up being a dead canary, the Republicans will start sweating."

The National Republican Congressional Committee has spent $2 million on ads criticizing Busby as too liberal. One spot claimed that as a school board member, she praised a teacher arrested in a child-pornography case for always being "willing to lend a hand."

The spot was pulled, but the claim has resurfaced in a Republican-paid mailer, which shows two teenage boys, an overturned car, a foamy glass of beer and asks: "Which is more irresponsible, a teenager or a politician?"

The Democratic Congressional Campaign Committee has countered with at least $1.3 million in ads criticizing Bilbray, who has worked as a lobbyist since losing his House seat in 2000. A recent spot accused him of missing votes to take a special-interest-paid trip to Australia, with a bouncing kangaroo wishing Bilbray "G'day."

Illegal immigration looms large in a district some 30 miles from the Mexican border.

Bilbray favors legislation that would make being in the country illegally a felony, criminalize people who help illegal immigrants and build a fence along the U.S.-Mexico border. He has held joint appearances in San Diego with Rep. James Sensenbrenner, R-Wis., the proponent of the hardline House measure.

Bilbray has criticized Busby for backing an effort favored by Bush and moderate Republicans that would give illegal immigrants in the United States a path toward citizenship. "Busby supports amnesty," Bilbray says in his ads.

In debates, Busby has pressed Bilbray on what he intends to do with the 11 million illegal immigrants already in the country.

Democrats recently accused Bilbray of lying about his home address to register in the district. Bilbray, who owns a home elsewhere in the San Diego area and one in Virginia that he bought while in Congress, reregistered at his mother's Carlsbad address little more than a week after the Cunningham scandal broke last year.

"Scandal usually has to attach to the candidate, but it becomes part of the background noise and drags on Bilbray," said Carl Luna, a political scientist at San Diego's Mesa College.

Bilbray, 55, who once commandeered a bulldozer to draw attention to Mexican sewage flowing over the border, has campaigned as a tax-cutter. He frequently reminds voters that he would return to Congress with seven years' seniority.

House Speaker Dennis Hastert, R-Ill., has campaigned for him, and Sen. John McCain, R-Ariz., is scheduled to travel to the district at the end of the month.

Bilbray won the Republican nomination in April with fewer than 1,000 votes separating him from a conservative challenger. Besides the runoff election in June, Bilbray will face millionaire Bill Hauf in the GOP primary for the November contest.

Busby, who captured 44 percent of the vote, has been selective in seeking Democratic help as she tries to appeal to Republican swing voters. California Sen. Dianne Feinstein, a moderate Democrat, is slated to appear June 3 for a $2,100-a-person fundraiser.

"The Democrats have very little downside here — if they even come close, then they'll have come close in a seat that should have been a no-brainer for the Republicans," Luna said.