L.A. Mayor James Hahn and challenger Antonio Villaraigosa lined up an initial round of high-level endorsements on Thursday as they charged ahead into the campaign for the May 17 runoff.

Hahn won the endorsement of the Los Angeles Area Chamber of Commerce, while L.A. City Controller Laura Chick endorsed Villaraigosa.

The chamber, which endorsed Hahn four years ago, took the unusual step of endorsing him again in a voice vote without conducting candidate interviews. Chamber board chairman Chris Martin said that Hahn and Villaraigosa were known quantities and thus didn’t need to be brought in for separate interviews.

Martin cited several factors in the chamber’s decision, including the achievement of business tax reform (although others were the driving force), his successful campaign to defeat secession, moving the Los Angeles International Airport overhaul plan forward and building more affordable housing units.

Martin also said Hahn’s decision to bring in William Bratton as police chief and the drop in crime rates played a role in the chamber’s decision.

He added that the chamber has not yet decided whether to ask its members to contribute to the Hahn campaign; he did note that several chamber members made contributions to Hahn during the primary.

Meanwhile, Chick said her decision to endorse Villaraigosa whom she endorsed in the mayoral runoff four years ago was based on two main factors: Villaraigosa’s actions as a councilman to support the controller’s office and increasing dissatisfaction with Hahn’s response to her audits.

Last year, Villaraigosa was one of two councilmembers who introduced a motion to allocate funds to Chick’s office to set up a waste and fraud unit.

“Antonio has shown through his actions that he wants to see the controller’s office receive the tools its needs,” Chick said. “He will welcome audits coming from the controller’s office as road maps for needed and positive change.

“That’s in stark contrast with our current mayor, who greeted my audits with silence or even outright fighting against them,” Chick said. “He was an impediment.”

Chick endorsed Hahn for re-election two years ago, but last August withdrew her endorsement as her clashes with the mayor intensified. This past January Chick said she would not make an endorsement in the primary but would make one in the runoff.