Election in California a Cliffhanger

Bilbray said the key to his victory on Tuesday is for Republicans "to understand that any vote that is not for Brian is at least a half a vote for Busby."

The fissures within the Republican base have coincided with a sharp decline in Bush's job approval rating and in the number of people who believe the country is headed in the right direction.

"If it weren't for the broad discontent with current administration and Republicans in general, [Busby] wouldn't be running nearly as well," said Gary Jacobson, a professor of political science at the University of California at San Diego. Jacobson noted that since 1966, of the 195 congressional elections in California districts where Republicans held a voter registration advantage, Democrats won four.

Busby, who took 36 percent of the vote in her 2004 race against Cunningham, said there is considerable momentum behind her candidacy, thanks to a combination of Cunningham's transgressions and the national mood. Busby characterized the contest as a "window into what is going on in Congress and a wakeup call." She said, "We have the opportunity . . . to send a message from this district."

Bilbray, too, sees the race as a national referendum -- but on immigration, not corruption.

He has castigated Busby as well as many in his own party -- including the president and Arizona Sen. John McCain -- as too soft on illegal immigrants.

"The president and the Senate are very unpopular right now over the amnesty issue," Bilbray said.

McCain does, however, appear in a television ad (paid for by the NRCC) in which he endorses Bilbray, an attempt to persuade loosely affiliated GOP voters to back the former congressman.

History offers mixed messages on the predictive capacity of special elections.

In the spring of 1994, Republicans won special elections for historically Democratic seats in Oklahoma and Kentucky that presaged the fall elections that gave Republicans the majority.

A decade later, Democrats captured Republican seats in Kentucky and South Dakota in special elections but failed to convert those wins into larger national gains in November 2004.

Amy Walter, who analyzes House races for the nonpartisan Cook Political Report, offered a measured approach to finding meaning in Tuesday's elections.

"There is going to be a lot written about [California District 50] win, lose or draw," she said. "I just don't think the outcome changes the prevalent political environment, which is bad for Republicans."