Walker entered August with a more than 4-1 advantage over Burke in cash on hand - $7.1 million compared to $1.7 million. Burke's longshot primary challenger, state Rep. Brett Hulsey, of Madison, had $440.
Burke and Hulsey face each other in the Aug. 12 primary. Wisconsin state election officials on Tuesday predicted turnout would be just 15 percent.
Hulsey's lack of fundraising in July - he collected just two donations totaling $35 - further demonstrates how slight his chances are of upsetting Burke, a millionaire and former Trek Bicycle Corp. executive who has been racking up endorsements as she builds name recognition and campaigns across the state.
The most recent Marquette University poll released last month showed Burke to be in a dead heat with Walker, a potential 2016 Republican candidate for president.
Burke's latest campaign finance report, filed late Monday night, showed she raised about $502,000 through July 28. Walker raised more than twice as much, or about $1.2 million.
Since getting into the race in October, Burke has raised $6 million. Walker has brought in three times as much, $18.7 million, since winning his recall election in July 2012. Hulsey has raised $2,523 since he got into the race in April.
Burke has put about $430,000 of her own money into the race so far, but nothing since she put in $400,000 in December. Burke has said she will spend as much of her own money as necessary, but she has not given a specific amount.
Walker received the maximum $10,000 donations from a dozen individuals in July, including seven members of the Michels family that owns and operates Michels Corp., the state's largest construction company. That includes company president Patrick Michels and two vice presidents, Tim and Kevin. Tim Michels ran for the U.S. Senate as a Republican in 2004 and lost to Democrat Russ Feingold.
Other $10,000 donors to Walker in July included James Schloemer, chairman and CEO of Continental Properties Co., in Menomonee Falls and Carl Ruedebusch, president and CEO of Ruedebusch Development and Construction, in Madison.
Burke did not list any $10,000 donors in July. Her single largest contribution was $43,128 from the UAC Wisconsin State PAC.
Both Burke and Walker have been spending aggressively on television advertising across the state. Hulsey has not raised nearly enough money to run any ads to help bolster his name recognition.