Gov. Scott Walker spent $16 million on television advertising after Democrats and their allies began circulating recall petitions against him last fall.
Walker's campaign finance reports show Walker spent $33.4 million between Nov. 15 and June 30. More than $15.9 million of that went toward TV ads.
The governor's Democratic challenger, Tom Barrett, spent $6.6 million, including $4.2 million on TV, between March 30 and the end of June.
Democrats forced Walker and five other GOP officeholders into a recall over a number of contentious policies, including cuts to education and a plan stripping most public workers of nearly all their union rights.
Walker easily defeated Barrett in the June 5 election.