WASHINGTON (AP) June 3, 2006 — Immigration and its politically controversial cousin, amnesty, are co-starring in the closing act of a House race with national implications, a close and costly production in Republican-friendly San Diego.

In a conservative district roughly 30 miles from the Mexican border, Democrat Francine Busby is under attack from Republican Brian Bilbray and the House GOP, depicted as an advocate of amnesty for illegal immigrants.

''Busby even said she would protest making English our official language,'' says a GOP party ad. ''Even worse, Busby opposes tougher visa regulations that would make it harder for terrorists to enter the country.''

Busby is tied or slightly ahead in several recent polls after she and the Democrats fashioned a campaign around an anti-corruption theme the party hopes to ride to victory in this fall's midterm elections.

Its local appeal seems obvious in a race to succeed Republican Rep. Randy Cunningham, who resigned from Congress and went to jail for accepting bribes. And she routinely refers to her opponent, a former congressman, as ''lobbyist Bilbray.''

The Democratic Congressional Campaign Committee is running an ad that says Bilbray has taken thousands of dollars from Cunningham and his co-conspirator in the bribery scandal, a reference to campaigns Bilbray ran while serving in the House in the 1990s.

Immigration plays a role in the Democratic campaign, as well.

''Even lobbyist Bilbray's conservative opponent stated that Bilbray failed to pass any laws to stop illegal immigration during his 12 years as a career politician and lobbyist,'' Busby claims in a radio ad that began running on Wednesday. She disputes advocating amnesty, and has used the words of Republican Sen. John McCain of Arizona to buttress her case.

Whatever the outcome of Tuesday's vote, Democrats are already claiming victory.

''We've already shown that the message of change versus the status quo is especially salient, even in very Republican districts,'' said Bill Burton, a spokesman for the DCCC. The organization has spent nearly $2 million to win the seat.

It's a theme Democrats have vowed to use in races stretching from upstate New York to Columbus, Ohio, and Albuquerque, N.M., in their drive to win control of the House this fall. They need to gain 15 seats for a majority.

Carl Forti, a spokesman for the House GOP committee, said Republicans intend to base their campaign strategy on local issues. The party group has criticized Busby as a liberal prone to raising taxes, citing her record as a school board member.

''We've long maintained, change only works in a district where corruption has been a problem as it was in'' the race to succeed Cunningham, countered Forti. ''If that's a message Democrats intend to take in November, we're probably going to do very well.''

As a measure of concern, the GOP campaign committee has spent nearly $4 million trying to retain the seat, an unprecedented amount made all the more striking given the Republican nature of the area. Cunningham dispatched Busby with ease in 2004, winning 58 percent of the vote, and President Bush won 55 percent en route to re-election.

Vice President Dick Cheney has been in to campaign and Speaker Dennis Hastert, R-Ill., met privately this spring with one of Bilbray's primary rivals, helping to persuade him to abandon a potential third-party race.

McCain, too, agreed to campaign for Bilbray, but he abruptly canceled a recently scheduled visit when Republican strategists decided it might cause Bilbray political problems. McCain, a strong draw for GOP voters, is also a leading supporter of legislation that recently passed the Senate. The bill combines enhanced border security with a guest worker program and a shot at citizenship for many of the illegal immigrants in the country.

Busby supports the bill, and even before the visit was canceled, stressed her position. McCain issued a written statement of support for Bilbray in place of his trip, sent him a check and is expected to record an endorsement message to be telephoned to thousands of voters in the district.

At the same time, Busby is hoping the presence of another rival will siphon off conservative votes that Bilbray needs -- and that immigration will be the Republican's undoing.

''Independent William Griffith is endorsed by the San Diego Minutemen and San Diego Border Alert because he opposes guest worker programs, amnesty and the hiring of illegal immigrants,'' she said in one recent ad.

Bilbray's Web Site calls for several steps related to immigration, including construction of a fence ''from the Pacific Ocean to the Gulf of Mexico,'' and banning ''illegal aliens from any access to Social Security benefits.'' It does not oppose a guest worker program and offers no plan for treatment of the estimated 11 million to 12 million illegal immigrants currently in the country.