In a sign of turmoil in Wendy Greuel’s campaign for Los Angeles mayor, her field director and three others resigned this week after an abrupt shift in strategy to turn out supporters in the May runoff against rival Eric Garcetti.

All four of those who quit were veterans of the high-tech operation used in President Obama’s reelection campaign. They specialize in mining data to target likely supporters and persuade them to vote, a crucial task in close, low-turnout elections.

In a statement Friday, Greuel, the city controller, said she was expanding her field team by hiring consultant Sue Burnside, who worked on Greuel’s previous City Council and controller campaigns. She did not mention the departure of the former Obama operatives: field director Stacy Cohen, data director Joe Kavanagh and regional field directors Maya Hutchinson and Marisa Kanof.

“After a strong campaign operation in the primary, we are taking our field program to the next level and expanding citywide,” Greuel said. Her campaign did not respond to email and voicemail requests for comment on the resignations.

Strong field operations take months to assemble and refine. It is unusual to replace the leaders of a field team in the final weeks before an election.

Parke Skelton, a campaign strategist unaligned in the mayor’s race, described the changes in Greuel’s campaign as “extraordinary.”

“To adopt a new field strategy two months out seems like a recipe for dysfunction to me,” he said. “The mistake may have been in assuming that the kind of massive volunteer operation that you saw in the Obama campaign could be replicated in a municipal election in Los Angeles, where less than 20% of the voters care enough to vote.”

Burnside, who did not return a call for comment, deploys teams of paid canvassers to call voters and visit them at their homes. Obama’s operation was built around volunteers.

The departure of Cohen and the three others came as Greuel has been struggling to project a consistent message on key issues, including how she would address rising pension and healthcare costs for the city workforce.

Cohen served as Obama’s California field director. She oversaw a network of tens of thousands of volunteers who made millions of calls to voters in Ohio, Colorado, Nevada and other battleground states.

Greuel finished second to Garcetti, a city councilman, in the March 5 primary election.

Cohen said Greuel’s get-out-the-vote operation in the first-round contest “was very successful and very positive. I wish Wendy and everybody in the campaign the best of success with everything.”

She added that Greuel’s senior strategy team “wanted to do a different program that I couldn’t provide for them.” Kavanagh, who was the Obama campaign’s California data director, said Greuel’s advisors “decided to go with a different field strategy in the general election, and I resigned from the campaign since that didn’t fit the strategy that I normally work in.” He declined to elaborate, citing a confidentiality agreement with Greuel’s campaign.

Obama’s successful use of cutting-edge technology in building volunteer networks and gaining support through social media and targeted advertising put his 2008 and 2012 campaign operatives in high demand. Mary Jane Stevenson, the California director of Obama’s reelection campaign, is co-founder of a group that plans to spend hundreds of thousands of dollars running an independent field operation for Garcetti.

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Twitter: @finneganlatimes

michael.finnegan@latimes.com