For months, the governor’s race in Virginia has unfolded beneath a cloud of scandal over the Republican incumbent that spread to his would-be Republican successor, Kenneth T. Cuccinelli II.

But now a potential scandal also threatens to distract the campaign of the Democratic candidate, Terry McAuliffe.

An electric car company Mr. McAuliffe founded is a target of an investigation by the Securities and Exchange Commission, government documents show.

The venture, GreenTech Automotive, was already a flash point because of the failure of enthusiastic promises of jobs made by Mr. McAuliffe, the former Democratic fund-raiser known for his showmanship and close friendship with Bill and Hillary Rodham Clinton.