Ben Carson’s presidential campaign is burning through cash

October was the best month of Ben Carson’s presidential campaign. A nine-point lead in Iowa by Halloween had his top aide crowing on Facebook FB 0.70 % about “Carson fever” gripping the country.

Behind the scenes, things weren’t going as well.

Internal campaign budget documents reviewed by The Wall Street Journal show a political operation hemorrhaging cash. Mr. Carson’s team raised $8.8 million in October and spent $9.5 million—putting the retired neurosurgeon’s effort under water months before the first early-state voters caucus and cast ballots.

The budget documents also undermine the Carson campaign’s Nov. 1 claim that it raised $10 million in October—a figure Mr. Carson himself talked up on Twitter.

“Carson fever has officially become an epidemic,” campaign manager Barry Bennett said in a Nov. 3 Facebook video.