Defending himself in a debate Thursday night, Wisconsin Republican Senate contender Tommy Thompson dramatically underestimated the amount of stock he owned in companies that do business with Iran or help its nuclear programs.

Challenged on his holdings by Democratic opponent Rep. Tammy Baldwin after The Huffington Post revealed one the companies in which Thompson invested is a partner with Iran in uranium mining, Thompson said he sold his shares as soon as he learned about it that day.

HuffPost had reached out to the Thompson campaign for comment but got no reply. That didn't come until the debate, when Baldwin brought up the report.

"I did not know about the fact that my stockbroker had purchased two shares, two company stocks," Thompson said. "I sold it. I sold it today. I found out today and I sold it today."

But Thompson owned more than two shares, and shares in more than two companies. It was actually five companies, and up to 800 shares worth up to $50,000.

According to his personal financial disclosure, he owned up to $1,000 worth of stock in the China National Offshore Oil Corporation, Gazprom and the China National Petroleum Corporation. All were cited in a recent Government Accountability Office study as having done business with Iran.

Gazprom appears to own a 49 percent stake in the firm Atomstroyexport, which is building Iran's nuclear reactor.

At Thursday's stock price closing, Thompson would have owned up to 100 shares of Gazprom, and up to five shares of CNOOC.

Thompson owned potentially more significant stakes in Royal Dutch Shell -- between $3,000 and $17,000, based on the ranges disclosed -- totaling between 43 and 245 shares.

He also held between $1,000 and $15,000 worth of stock in oil services firm Schlumberger, which would have amounted to between 13 and 200 shares. Schlumberger has been probed by the Justice Department over its Iran work.

Lastly, Thompson owned between $1,000 and $15,000 worth of stock in Rio Tinto, a firm that partners with Iran in a uranium mine in Namibia. The value of Thompson's holdings in Rio Tinto translates to between 19 and 288 shares.

Thompson did not specify which stocks he sold. His spokeswoman, Lisa Boothe, later told reporters: "Gov. Thompson took decisive action when he became aware of stocks his financial adviser purchased. He rid himself of them as soon as he found out they had any business dealings with Iran, no matter how minor. The governor is actively reviewing all of his investments to ensure that he does not invest in a company that does business with Iran."

At a minimum, based on the ranges reported, Thompson's total investment in an Iran-linked portfolio was worth more than $5,000, and comprised more than 80 shares.

Baldwin raised the stock ownership because Thompson had accused her of being to friendly to Iran.

Also on HuffPost:

Loading Slideshow...
  • Vice President Joe Biden and Republican vice presidential nominee Rep. Paul Ryan of Wisconsin shake hands after the vice presidential debate at Centre College, Thursday, Oct. 11, 2012, in Danville, Ky. (AP Photo/Pool-Michael Reynolds)

  • Vice President Joe Biden and Republican vice presidential nominee Rep. Paul Ryan of Wisconsin shake hands after the vice presidential debate at Centre College, Thursday, Oct. 11, 2012, in Danville, Ky. (AP Photo/Pool-Michael Reynolds)

  • Vice President Joe Biden and Republican vice presidential nominee Rep. Paul Ryan of Wisconsin gesture after the vice presidential debate at Centre College, Thursday, Oct. 11, 2012, in Danville, Ky. (AP Photo/Pool-Michael Reynolds)

  • Vice President Joe Biden and Republican vice presidential nominee Rep. Paul Ryan of Wisconsin gesture after the vice presidential debate at Centre College, Thursday, Oct. 11, 2012, in Danville, Ky. (AP Photo/Pool-Michael Reynolds)

  • Joe Biden, Paul Ryan

    Vice President Joe Biden, left, and Republican vice presidential nominee Rep. Paul Ryan, of Wisconsin, shake hands following their the vice presidential debate at Centre College, Thursday, Oct. 11, 2012, in Danville, Ky. (AP Photo/David Goldman)

  • Joe Biden, Paul Ryan

    Vice President Joe Biden and Republican vice presidential nominee Rep. Paul Ryan of Wisconsin shake hands after the vice presidential debate at Centre College, Thursday, Oct. 11, 2012, in Danville, Ky. (AP Photo/Charlie Neibergall)

  • Joe Biden, Jill Biden

    Vice President Joe Biden kisses his wife, Jill Biden, following the vice presidential debate with Republican vice presidential nominee Rep. Paul Ryan, of Wisconsin, at Centre College, Thursday, Oct. 11, 2012, in Danville, Ky. (AP Photo/David Goldman)

  • Vice President Joe Biden talks to Janna Ryan, wife of Republican vice presidential nominee Rep. Paul Ryan of Wisconsin after the vice presidential debate at Centre College, Thursday, Oct. 11, 2012, in Danville, Ky. (AP Photo/Pool-Michael Reynolds)

  • Paul Ryan, Janna Ryan

    Republican vice presidential nominee, Rep. Paul Ryan, of Wisconsin, kisses his wife Janna following the vice presidential debate with Vice President Joe Biden at Centre College, Thursday, Oct. 11, 2012, in Danville, Ky. (AP Photo/David Goldman)

  • Republican vice presidential nominee Rep. Paul Ryan's wife Janna, left, shakes hands with Jill Biden, wife of Vice President Joe Biden, following the vice presidential debate at Centre College, Thursday, Oct. 11, 2012, in Danville, Ky. (AP Photo/David Goldman)

  • Joe Biden

    Vice President Joe Biden listens to Republican vice presidential nominee Rep. Paul Ryan, of Wisconsin, during the vice presidential debate at Centre College, Thursday, Oct. 11, 2012, in Danville, Ky. (AP Photo/Eric Gay)

  • Paul Ryan

    Republican vice presidential nominee Rep. Paul Ryan of Wisconsin answers a question during the vice presidential debate at Centre College, Thursday, Oct. 11, 2012, in Danville, Ky. (AP Photo/Charlie Neibergall)

  • Paul Ryan, Joe Biden

    Republican vice presidential nominee Rep. Paul Ryan, of Wisconsin, right, listens to Vice President Joe Biden during the vice presidential debate at Centre College, Thursday, Oct. 11, 2012, in Danville, Ky. (AP Photo/Eric Gay)

  • Paul Ryan

    Republican vice presidential nominee Rep. Paul Ryan of Wisconsin answers a question during the vice presidential debate at Centre College, Thursday, Oct. 11, 2012, in Danville, Ky. (AP Photo/Charlie Neibergall)

  • Vice President Joe Biden and Republican vice presidential nominee Rep. Paul Ryan of Wisconsin participate in the vice presidential debate at Centre College, Thursday, Oct. 11, 2012, in Danville, Ky. (AP Photo/Pool-Rick Wilking)

  • Vice President Joe Biden and Republican vice presidential nominee Rep. Paul Ryan of Wisconsin participate in the vice presidential debate at Centre College, Thursday, Oct. 11, 2012, in Danville, Ky. (AP Photo/Pool-Rick Wilking)

  • Paul Ryan, Joe Biden

    Republican vice presidential nominee Rep. Paul Ryan, of Wisconsin, right, and Vice President Joe Biden discuss a point during the vice presidential debate at Centre College, Thursday, Oct. 11, 2012, in Danville, Ky. (AP Photo/David Goldman)

  • Vice President Joe Biden and Republican vice presidential nominee Rep. Paul Ryan of Wisconsin participate in the vice presidential debate at Centre College, Thursday, Oct. 11, 2012, in Danville, Ky. (AP Photo/Pool-Rick Wilking)

  • Paul Ryan, Joe Biden, Martha Raddatz

    Republican vice presidential nominee Rep. Paul Ryan, of Wisconsin, right, and Vice President Joe Biden, center, listen to moderator Martha Raddatz during the vice presidential debate at Centre College, Thursday, Oct. 11, 2012, in Danville, Ky. (AP Photo/David Goldman)

  • US-VOTE-2012-DEBATE

    A combination picture of the vice presidential debate between US Vice President Joe Biden (L) and Republican vice presidential candidate Paul Ryan (R) at the Norton Center at Centre College in Danville, Kentucky, October 11, 2012, moderated by Martha Raddatz of ABC News. AFP PHOTO / Saul LOEB (Photo credit should read SAUL LOEB/AFP/GettyImages)

  • Vice President Joe Biden and Republican vice presidential nominee Rep. Paul Ryan of Wisconsin participate in the vice presidential debate at Centre College, Thursday, Oct. 11, 2012, in Danville, Ky. (AP Photo/Pool-Michael Reynolds)

  • Vice President Joe Biden answers a question during the vice presidential debate at Centre College, Thursday, Oct. 11, 2012, in Danville, Ky. (AP Photo/Pool-Michael Reynolds)

  • Paul Ryan

    Republican vice presidential nominee Rep. Paul Ryan, of Wisconsin, makes a point to Vice President Joe Biden during the vice presidential debate at Centre College, Thursday, Oct. 11, 2012, in Danville, Ky. (AP Photo/Eric Gay)

  • Joe Biden, Paul Ryan

    Vice President Joe Biden and Republican vice presidential nominee Rep. Paul Ryan of Wisconsin answer a question during the vice presidential debate at Centre College, Thursday, Oct. 11, 2012, in Danville, Ky. (AP Photo/Charlie Neibergall)

  • US-VOTE-2012-DEBATE

    US Vice President Joe Biden (L) and Republican vice presidential candidate Paul Ryan (R) participate in the vice presidential debate at the Norton Center at Centre College in Danville, Kentucky, October 10, 2012, moderated by Martha Raddatz (C) of ABC News. AFP PHOTO / Saul LOEB (Photo credit should read SAUL LOEB/AFP/GettyImages)

  • US-VOTE-2012-DEBATE

    US Vice President Joe Biden (L) and Republican vice presidential candidate Paul Ryan (R) participate in the vice presidential debate at the Norton Center at Centre College in Danville, Kentucky, October 10, 2012, moderated by Martha Raddatz (C) of ABC News. AFP PHOTO / Saul LOEB (Photo credit should read SAUL LOEB/AFP/GettyImages)

  • US-VOTE-2012-DEBATE

    US Vice President Joe Biden participates in the vice presidential debate with Republican vice presidential candidate Paul Ryan (out of frame) at the Norton Center at Centre College in Danville, Kentucky, October 10, 2012. AFP PHOTO / Saul LOEB (Photo credit should read SAUL LOEB/AFP/GettyImages)

  • US-VOTE-2012-DEBATE

    US Vice President Joe Biden (L) and Republican vice presidential candidate Paul Ryan (R) participate in the vice presidential debate at the Norton Center at Centre College in Danville, Kentucky, October 10, 2012, moderated by Martha Raddatz (C) of ABC News. AFP PHOTO / Saul LOEB (Photo credit should read SAUL LOEB/AFP/GettyImages)

  • US-VOTE-2012-DEBATE

    US Vice President Joe Biden (L) and Republican vice presidential candidate Paul Ryan (R) participate in the vice presidential debate at the Norton Center at Centre College in Danville, Kentucky, October 10, 2012, moderated by Martha Raddatz (C) of ABC News. AFP PHOTO / Saul LOEB (Photo credit should read SAUL LOEB/AFP/GettyImages)

  • Paul Ryan

    Republican vice presidential nominee, Rep. Paul Ryan, of Wisconsin, speaks during the vice presidential debate at Centre College, Thursday, Oct. 11, 2012, in Danville, Ky. (AP Photo/David Goldman)

  • Vice President Joe Biden speaks during the vice presidential debate with Republican vice presidential nominee Rep. Paul Ryan, of Wisconsin, at Centre College, Thursday, Oct. 11, 2012, in Danville, Ky. (AP Photo/David Goldman)

  • Jill Biden, Beau Biden, Hunter Biden

    Jill Biden, center, wife of Vice President Joe Biden, sits with her sons Beau Biden, left, and Hunter Biden, right, before the start of the vice presidential debate, at Centre College in Danville, Ky., Thursday, Oct. 11, 2012. (AP Photo/Pablo Martinez Monsivais)

  • Paul Ryan

    Republican vice presidential nominee Rep. Paul Ryan of Wisconsin answers a question during the vice presidential debate at Centre College, Thursday, Oct. 11, 2012, in Danville, Ky. (AP Photo/Charlie Neibergall)

  • US-VOTE-2012-DEBATE

    US Vice President Joe Biden (L) and Republican vice presidential candidate Paul Ryan (R) participate in the vice presidential debate at the Norton Center at Centre College in Danville, Kentucky, October 10, 2012, moderated by Martha Raddatz (C) of ABC News. AFP PHOTO / Saul LOEB (Photo credit should read SAUL LOEB/AFP/GettyImages)

  • US-VOTE-2012-DEBATE

    US Vice President Joe Biden (L) and Republican vice presidential candidate Paul Ryan (R) participate in the vice presidential debate at the Norton Center at Centre College in Danville, Kentucky, October 10, 2012, moderated by Martha Raddatz (C) of ABC News. AFP PHOTO / Saul LOEB (Photo credit should read SAUL LOEB/AFP/GettyImages)

  • US-VOTE-2012-DEBATE

    US Vice President Joe Biden (L) and Republican vice presidential candidate Paul Ryan (R) participate in the vice presidential debate at the Norton Center at Centre College in Danville, Kentucky, October 10, 2012, moderated by Martha Raddatz (C) of ABC News. AFP PHOTO / Saul LOEB (Photo credit should read SAUL LOEB/AFP/GettyImages)

  • Vice President Joe Biden answers a question during the vice presidential debate at Centre College, Thursday, Oct. 11, 2012, in Danville, Ky. (AP Photo/Pool-Rick Wilking)

  • Republican vice presidential nominee Rep. Paul Ryan of Wisconsin answers a question during the vice presidential debate at Centre College, Thursday, Oct. 11, 2012, in Danville, Ky. (AP Photo/Pool-Michael Reynolds)

  • Joe Biden

    Vice President Joe Biden reacts to a question during the vice presidential debate at Centre College, Thursday, Oct. 11, 2012, in Danville, Ky. (AP Photo/Charlie Neibergall)

  • Joe Biden, Paul Ryan

    Vice President Joe Biden, left, and Republican vice presidential nominee, Rep. Paul Ryan, of Wisconsin, challenge each other during the vice presidential debate at Centre College, Thursday, Oct. 11, 2012, in Danville, Ky. (AP Photo/Eric Gay)

  • Republican vice presidential nominee Rep. Paul Ryan of Wisconsin watches as Vice President Joe Biden answers a question during the vice presidential debate at Centre College, Thursday, Oct. 11, 2012, in Danville, Ky. (AP Photo/Pool-Rick Wilking)

  • Vice President Joe Biden and Republican vice presidential nominee Rep. Paul Ryan of Wisconsin participate in the vice presidential debate at Centre College, Thursday, Oct. 11, 2012, in Danville, Ky. (AP Photo/Pool-Rick Wilking)

  • Joe Biden

    Vice President Joe Biden answers a question during the vice presidential debate at Centre College, Thursday, Oct. 11, 2012, in Danville, Ky. (AP Photo/Charlie Neibergall)

  • Joe Biden, Paul Ryan

    Vice President Joe Biden, left, and Republican vice presidential nominee Rep. Paul Ryan, of Wisconsin, respond to moderator Martha Raddatz during the vice presidential debate at Centre College, Thursday, Oct. 11, 2012, in Danville, Ky. (AP Photo/Eric Gay)

  • Janna Ryan, Ted Olson, Lady Booth Olson, Betty Douglas

    Janna Ryan, second from right, wife of Republican vice presidential candidate, Rep. Paul Ryan, R-Wis., his mother Betty Douglas, Ted Olson, second from left, former solicitor-general of the U.S. and his wife Lady Booth Olson sit in the audience before he start of the vice presidential debate, Thursday, Oct. 11, 2012, at Centre College in Danville, Ky. (AP Photo/Mary Altaffer)

  • US-VOTE-2012-DEBATE

    US Vice President Joe Biden participates in the vice presidential debate with Republican vice presidential candidate Paul Ryan (out of frame) at the Norton Center at Centre College in Danville, Kentucky, October 10, 2012, moderated by Martha Raddatz of ABC News. AFP PHOTO / Saul LOEB (Photo credit should read SAUL LOEB/AFP/GettyImages)

  • US-VOTE-2012-DEBATE

    Republican vice presidential candidate Paul Ryan (R) participates in the vice presidential debate with US Vice President Joe Biden (out of frame) at the Norton Center at Centre College in Danville, Kentucky, October 10, 2012, moderated by Martha Raddatz (L) of ABC News. AFP PHOTO / Saul LOEB (Photo credit should read SAUL LOEB/AFP/GettyImages)

  • US-VOTE-2012-DEBATE

    Republican vice presidential candidate Paul Ryan (R) participates in the vice presidential debate with US Vice President Joe Biden (out of frame) at the Norton Center at Centre College in Danville, Kentucky, October 10, 2012, moderated by Martha Raddatz (L) of ABC News. AFP PHOTO / Saul LOEB (Photo credit should read SAUL LOEB/AFP/GettyImages)

  • Vice President Joe Biden answers a question during the vice presidential debate at Centre College, Thursday, Oct. 11, 2012, in Danville, Ky. (AP Photo/Pool-Michael Reynolds)