The two candidates for Los Angeles mayor, who agree broadly on many issues, disagree strenuously about one: how to fix the city's aging and congested airport.
His opponent, Antonio Villaraigosa, was one of three council members to vote against the controversial plan, although he never has detailed his own vision of what to do with the 76-year-old airport.
The issue has played a below-the-radar role in the campaign, but could have a major impact on whether Hahn is able to win a second term.
Opposition to the mayor's plan remains intense in airport-area communities, including Westchester and Playa del Rey, and many residents say Villaraigosa's vote against it is enough to win their support. The councilman has landed endorsements from influential politicians representing the airport area.
A significant bloc of voters resides in those older communities, where the city of Los Angeles hugs the northern boundary of the airport. The largely residential region, home to many retirees, is a Republican stronghold that has historically favored candidates who are more conservative on social issues.
In the 2001 mayoral runoff, 57% in the area voted for Hahn and 41% for Villaraigosa. But in March, Villaraigosa pulled ahead, receiving 29% of the vote, with former Assembly Speaker Bob Hertzberg getting 25% and Hahn coming in third with 24%.
Villaraigosa said in an interview that he would not kill Hahn's plan if he became mayor, explaining that he supports what are known as the "green-light" projects, which are slated for the first phase of construction. Those include moving the airport's southernmost runway 55 feet closer to El Segundo, and building a consolidated rental car center in Lot C and a transit hub near the Century Freeway.
But he opposes the so-called "yellow-light" projects, including a controversial check-in facility at Manchester Square, a Westchester neighborhood near the San Diego Freeway, and tearing down Terminals 1, 2 and 3.
Under Hahn's plan, those projects would be built in a second phase and subject to further environmental, security and traffic analyses. Villaraigosa said he intends to "permanently put them on the proverbial shelf."
The councilman's reticence to release his own LAX plan, however, has left some airport-area residents wary of what he would do at the airport if he won the May 17 runoff.
"I hear people talking about being in favor of Villaraigosa because he's made this promise to stop airport expansion," said Geoff Maleman, who lives in Westchester. "But in some ways, I think it's an uninformed position because no one knows where Antonio stands on the airport."
Some legal experts contend that the extensive environmental studies for Hahn's plan rely on the check-in center to absorb additional traffic and to make the air-quality analysis work.
If the check-in center were shelved, as Villaraigosa wants, the city could be forced to redo those studies -- a process that could take up to two years.
"If he just goes ahead with the green-light projects and does away with the yellow-light projects, then in essence he doesn't have a project and has to start over," said Barbara Lichman, an attorney representing Los Angeles County, which together with Inglewood and Culver City sued the city of Los Angeles to stop the long-awaited airport overhaul.
In addition, the yellow-light projects include a plan to decrease the number of gates where airplanes park from 163 to 153, which is how Hahn intends to hold growth at LAX to 78.9 million annual passengers.
Villaraigosa takes issue with the contention that doing away with the controversial check-in center would cause the plan's 30,000-page environmental analysis to unravel.
"I think there's a disagreement among the lawyers about how to proceed," he said. "I don't frankly trust that this administration has given us the straight answers on that issue."
The two-phase approach was devised by Councilwoman Cindy Miscikowski, who represents the airport area and is a staunch supporter of the mayor. She says that her decision to support him was based in part on his willingness to listen to her ideas about how to alter his airport plan.
Villaraigosa said, however, that he has received endorsements from Reps. Maxine Waters (D-Los Angeles) and Jane Harman (D-Venice), who represent the area in Congress, partly because he has committed to dumping the check-in center and not expanding passenger capacity at LAX.
"Clearly, we share common opposition to LAX expansion and a steadfast belief that the residents living in and around the airport have every right to expect Jim Hahn to keep his promise not to expand airport capacity at LAX," Villaraigosa said.
When he was running for mayor in 2001, Hahn signed a pledge to keep LAX at the maximum capacity allowed by the existing facilities -- or 78 million annual passengers. But critics argue that Hahn's plan would allow the airport to grow to at least 89 million travelers a year.
The mayor disputes that.
"If you read the so-called pledge and the master plan, it's plain that he kept his word," said Kam Kuwata, a Hahn campaign strategist.
Hahn introduced his LAX plan in the weeks following the Sept. 11 terrorist attacks, saying it favored safety and security over expansion.
Environmental documents for the mayor's plan built on studies already completed for Mayor Richard Riordan's airport proposal. The city has spent 10 years and $147 million trying to devise a blueprint to update LAX.
Waters and Assemblyman Mike Gordon (D-El Segundo), who also recently endorsed Villaraigosa, don't believe Hahn's proposal would hold LAX to 78 million annual passengers.
"We're impacted by noise and traffic and pollution, and we're interested in that airport being secure," Waters said when she endorsed the councilman. "And we think there are a number of things we can do to make it a better place, to make it more secure, but we don't need this expansion, and that's a big issue with me. That's No. 1 with me."
Some influential Westchester residents who voted for Hahn in 2001 because they didn't like Riordan's expansion plan agree with Waters and are planning not only to vote for Villaraigosa, but to raise money for him.
"In looking each other in the eye, he assured me that he was not only avidly against [Hahn's plan], but in particular the Manchester Square portion," said Howard Drollinger, a Westchester developer who manages 1.3 million square feet of commercial space in the community.
The businessman, together with the Alliance for a Regional Solution to Airport Congestion -- a local group opposed to Hahn's LAX plan -- will hold a fundraiser for Villaraigosa on Wednesday in Westchester. The group also is paying in part for a mailer that touts the councilman's position on LAX.
Neighborhood associations in Westchester are using phone banks to call residents and urge them to vote for Villaraigosa and walking the area on his behalf.
"In this community, the airport issue is in a lot of ways a singular determinant for how people will vote," Maleman said. "There are a number of people who voted for Hahn thinking his plan will be better than Riordan's. Now that they saw the Hahn plan, they're voting for Villaraigosa. Then Villaraigosa will come up with a plan, and people will vote against him because it isn't good enough."
Times researcher Maloy Moore contributed to this report.